An ultra-high gain and efficient amplifier based on Raman amplification in plasma

Raman amplification arising from the excitation of a density echelon in plasma could lead to amplifiers that significantly exceed current power limits of conventional laser media. Here we show that 1-100 J pump pulses can amplify picojoule seed pulses to nearly joule level. The extremely high gain also leads to significant amplification of backscattered radiation from "noise", arising from stochastic plasma fluctuations that competes with externally injected seed pulses, which are amplified to similar levels at the highest pump energies. The pump energy is scattered into the seed at an oblique angle with 14 J sr-1, and net gains of more than eight orders of magnitude. The maximum gain coefficient, of 180 cm-1, exceeds high-power solid-state amplifying media by orders of magnitude. The observation of a minimum of 640 J sr-1 directly backscattered from noise, corresponding to ≈10% of the pump energy in the observation solid angle, implies potential overall efficiencies greater than 10%.

Raman amplification in the coherent wave-breaking regime

In regimes far beyond the wave-breaking threshold of Raman amplification, we show that significant amplification can occur after the onset of wave breaking, before phase mixing destroys the coherent coupling between pump, probe, and plasma wave. Amplification in this regime is therefore a transient effect, with the higher-efficiency "coherent wave-breaking" (CWB) regime accessed by using a short, intense probe. Parameter scans illustrate the marked difference in behavior between below wave breaking, in which the energy-transfer efficiency is high but total energy transfer is low, wave breaking, in which efficiency is low, and CWB, in which moderate efficiencies allow the highest total energy transfer.

Fast multidimensional model for the simulation of Raman amplification in plasma

We present Leap, a simulation model for Raman amplification in plasma, combining an envelope treatment of the laser fields with an electrostatic particle-in-cell solver. The code is fully two dimensional, with the model readily extendible to three dimensions, and includes dispersive and refractive effects. Simulations carried out for Raman amplification in a plasma channel show that guiding of both the pump and the probe contribute to the evolution of the probe, resulting in a shorter, more intense pulse.

Resection of the lesion in patients with hypothalamic hamartomas and catastrophic epilepsy

BACKGROUND

Patients with hypothalamic hamartomas (HH) often have severe refractory epilepsy, incapacitating behavioral abnormalities, and cognitive decline. Attempts to control the seizure disorder by resection of apparently epileptogenic mesial temporal or other cortical structures have failed consistently.

OBJECTIVE

To report a series of 13 patients in whom the hamartoma itself was resected.

METHODS

All patients underwent preoperative evaluation between ages 2 and 33 years and had subtotal or complete resection of the hamartoma. Follow-up ranged from 1 to 5.5 years (mean: 2.8 y).

RESULTS

Preoperatively, all patients had variable combinations of gelastic, complex partial, and generalized seizures. Eight had drop attacks. In addition, all had marked behavior abnormalities and cognitive impairment. Postoperatively, two patients are completely seizure-free and 11 are either seizure-free or have achieved a greater than 90% reduction of drop attacks and generalized tonic-clonic seizures. However, minor gelastic, complex partial, and atypical absence seizures have persisted in 11 patients, although at significantly reduced rates. In addition, there has been a dramatic improvement in behavior and cognition. Three patients had an anterior thalamic and one a capsular infarct, which left only minimal long-term deficits. Exact location of the lesion in relation to the interpeduncular fossa and the walls of the third ventricle correlated with extent of excision, seizure control, and complication rate.

CONCLUSION

Resection can alleviate both the seizures and the behavioral and cognitive abnormalities of hypothalamic hamartomas, but complications are frequent.

Reliability of intraoperative electrophysiological monitoring in selective posterior rhizotomy

OBJECT

Selective posterior rhizotomy is a well-established treatment for spasticity associated with cerebral palsy. At most medical centers, responses of dorsal rootlets to electrical stimulation are used to determine ablation sites; however, there has been some controversy regarding the reliability of intraoperative stimulation. The authors analyzed data obtained from the McGill Rhizotomy Database to determine whether motor responses to dorsal root stimulation were reproducible.

METHODS

A series of 77 patients underwent selective dorsal rhizotomy at a single medical center. The dorsal roots from L-2 to S-2 were stimulated to determine the threshold amplitude. The roots were then stimulated at 2 to 4 times the highest threshold with a 1-second 50-Hz train. A second stimulation run of the entire dorsal root was performed before it was divided into rootlets. Rootlets were individually stimulated and sectioned according to the extent of abnormal electrophysiological propagation. Motor responses were recorded by electromyography and were also assessed by a physiotherapist, and grades of 0 to 4+ were assigned. The difference in grades between the first and second stimulation trains was determined for 752 roots. Statistical analysis demonstrated a clear consistency in motor responses between the two stimulation runs, both in the electromyographic readings and the physiotherapist's assessment. More than 93% of dorsal roots had either no change or a difference of only one grade between the two trials. Furthermore, the vast majority of dorsal roots assigned a grade of 4+ at the first trial maintained the same maximally abnormal electrophysiological response during the second stimulation run.

CONCLUSIONS

This study indicates that currently used techniques are reproducible and reliable for selection of abnormal rootlets. Intraoperative electrophysiological stimulation can be valuable in achieving a balance between elimination of spasticity and preservation of underlying strength.

Brainstem Gliomas. A 10-year institutional review

Case records of 37 patients with a diagnosis of brainstem glioma treated at the Montreal Children's Hospital from June 1989 to June 1999 were reviewed. 15 patients had diffuse pontine gliomas and 22 patients had focal forms of brainstem gliomas. The two groups were compared with respect to age, clinical evolution, radiological appearance, type of surgery practised, histological diagnosis, adjuvant treatments and survival. A non-pontine brainstem location, a cystic or exophytic component, bright enhancement with gadolinium injection, a histological diagnosis of pilocytic astrocytoma or ganglioglioma were favourable prognostic factors. Progression-free survival and overall survival were significantly worse in the group of patients with diffuse pontine gliomas. The relative impact of radical surgery and/or radiotherapy is analysed. Surgery coupled to adjuncts such as navigation, ultrasound and monitoring plays an important role for focal brainstem lesions. Focal/conformal radiotherapy has an adjuvant role but better treatments are needed for the diffuse pontine brainstem lesions.

Intractable epilepsy after a functional hemispherectomy: important lessons from an unusual case. Case report

Residual seizures after functional hemispherectomy occur in approximately 20% of patients with catastrophic epilepsy. These episodes are traditionally attributed to incomplete disconnection, persistent epileptogenic activity in the ipsilateral insular cortex, or bilateral independent epileptogenic activity. The authors report on the case of an 8-year-old boy with an intractable seizure disorder who had classic frontal adversive seizures related to extensive unilateral left hemispheric cortical dysplasia. The initial intervention consisted of extensive removal of the epileptic frontal and precentral dysplastic tissue and multiple subpial transections of the dysplastic motor strip, guided by intraoperative electrocorticography, Subsequently, functional hemispherectomy including insular cortex resection was performed for persistent attacks. After a seizure-free period of 6 months, a new pattern ensued, consisting of an aura of fear, dystonic posturing of the right arm, and unusual postictal hyperphagia coupled with an interictal diencephalic-like syndrome. Electroencephalography and ictal/interictal single-photon emission computerized tomography were used to localize the residual epileptic discharges to deep ipsilateral structures. Results of magnetic resonance imaging indicated a complete disconnection except for a strip of residual frontobasal tissue. Therefore, a volumetric resection of the epileptogenic frontal basal tissue up to the anterior commissure was completed. The child has remained free of seizures during 21 months of follow-up review. Standard hemispherectomy methods provide extensive disconnection, despite the presence of residual frontal basal cortex. However, rarely, and especially if it is dysplastic, this tissue can represent a focus for refractory seizures. This is an important consideration in determining the source of ongoing seizures posthemispherectomy in patients with extensive cortical dysplasia. It remains important to assess them fully before considering their disease refractory to surgical treatment.

Primitive neuroectodermal tumors of the brainstem: investigation of seven cases

OBJECTIVE

We discuss the clinical aspects, pathology, and molecular genetics of 7 patients with primitive neuroectodermal tumors (PNETs) arising in the brainstem that were treated at our institution from 1986 through 1995. Most neuro-oncologists avoid performing biopsies in children with pontine tumors. This article raises the question as to whether biopsies should be performed, because treatment recommendations might differ if a PNET was diagnosed rather than a pontine glioma.

PATIENTS AND METHODS

We reviewed the clinical neuro-oncology database and the files of the Division of Neuropathology at New York University Medical Center from 1986 through 1995 and identified 7 histologically confirmed PNETs arising in the brainstem among 146 pediatric brainstem tumors. The clinical, neuroradiological, and neuropathological data were reviewed. Postmortem examinations were performed in 2 cases. Formalin-fixed, paraffin-embedded tumor tissues were also available in 6 of 7 patients that were tested for p53 gene mutations using single-strand conformation polymorphism analysis. We also tested 9 cerebellar PNETs, 9 brainstem gliomas, and 3 normal brains for p53 gene mutations as controls.

RESULTS

All 7 patients presented with focal cranial nerve deficits, and 2 were also hemiparetic. The median age at diagnosis was 2.7 (1-8 years). Magnetic resonance imaging (MRI) characteristics included a focal intrinsic exophytic nonenhancing brainstem lesion that had low T1-weighted and high T2-weighted signals. Hydrocephalus was present in 5 patients at diagnosis, 3 of whom had leptomeningeal dissemination. Meningeal dissemination occurred later in the course of the disease in 3 other patients. Five children required shunts at diagnosis and another 2 at recurrence. Despite therapy, all 7 PNET patients died within 17 months of diagnosis with a mean survival of 8 (4-17) months. No mutation in the p53 gene was detected.

CONCLUSIONS

Brainstem PNETs tend to arise at a younger age than brainstem gliomas and medulloblastomas. The MRI pattern suggests a localized rather than a diffuse intrinsic nonenhancing brainstem tumor. Like other PNETs, brainstem PNETs have a high predilection to disseminate within the central nervous system. The absence of p53 mutations is similar to other PNETs. Despite their origin close to the cerebellum, brainstem PNETs exhibit a more aggressive behavior and result in worse clinical outcomes than do cerebellar PNETs.

Dysgenetic mesial temporal sclerosis: an unrecognized entity

Mesial temporal sclerosis (MTS) is the most frequently encountered lesion in adult patients with intractable temporal epilepsy; it is found in isolation in approximately two-thirds of surgically treated cases. Whereas the exact etiology of MTS is still controversial, several reports suggest that this pathologic lesion is both the cause and the consequence of chronic seizures and develops progressively during childhood secondary to recurrent seizures. In order to evaluate the clinical importance of MTS in children, we retrospectively reviewed the clinical charts of children who underwent surgery for medically intractable temporal epilepsy and report cases presenting an amygdalo-hippocampic dual pathology. Six children aged 1.5-16 years (mean +/- SD: 7.5 +/- 3 years) presenting with partial complex seizures (5 cases) or extension spasms (1 case), with onset from 6 months to the age of 8.5 years (mean seizure onset +/- SD: 3 +/- 5 years) underwent anterior temporal lobectomy including resection of the amygdala and hippocampus. All patients exhibited variable degrees of severity of neuronal loss and gliosis in the amygdala and/or hippocampus. The pathological picture of MTS was not isolated, however. Careful pathological examination has thus shown foci of amygdalo-hippocampic neuronal dysplasia in six patients, with concomitant bilaminated fascia dentata in two cases. Postoperatively, no mortality or morbidity was encountered. After a mean follow-up of 2.5 years, four patients are seizure free. One patient had a 80% rate of improvement in seizure frequency, though still having occasional febrile convulsions. In another patient, complex partial seizures resolved, but rare episodes of absence were still observed. These data are in keeping with the hypothesis that MTS could be secondary to repeated seizures. The analysis of this series of patients could suggest that mesiotemporal dysplastic lesions within the amygdalo-hippocampic structures induce seizures, which, in turn, will favor the development of MTS during childhood. MTS could then lead to synaptic reorganization, which can express abnormal hyperexcitability and result in more recurrent seizures. In this way a vicious circle is set up, which may explain the progression of seizures in some patients.

Tuberous sclerosis complex and neonatal seizures

Tuberous sclerosis complex is a multisystemic neurocutaneous disorder, manifesting variably during infancy and childhood that remains poorly described in neonates. When described in this population, tuberous sclerosis complex is most commonly associated with cardiac rhabdomyomas and brain tumors, but is rarely mentioned as an etiology for neonatal seizures. We report two children with tuberous sclerosis presenting for neonatal seizures. Neuroimaging findings of neonatal tuberous sclerosis complex are discussed. Given the absence of many of the traditional stigmata of tuberous sclerosis complex in the neonate, seizures should be considered an important presenting feature of this disorder in this particular age group.

Magnetic resonance imaging in children with voiding dysfunction: is it indicated?

PURPOSE

We evaluated the role of magnetic resonance imaging (MRI) of the lumbosacral spinal cord in children with complicated voiding dysfunction and normal neuro-orthopedic examination.

MATERIALS AND METHODS

We reviewed the records of 32 consecutive children with complicated enuresis who were referred for neurosurgical evaluation, including those with a history of refractory voiding dysfunction or incontinence associated with persistent vesicoureteral reflux, encopresis, or associated leg or back pain. Nine patients were excluded from study because of urethral or anorectal anomalies, or failure to meet the inclusion criteria. Eligible for study inclusion were 23 children with a mean age of 8.9 years. Complete neurological and orthopedic examinations were normal in all patients except 1 with mild scoliosis and 1 with congenital facial palsy.

RESULTS

Urodynamic studies revealed instability in 14 cases, hypertonia in 7, hyporeflexia in 2 and detrusor-sphincter dyssynergia in 4. Skeletal abnormalities, mostly spina bifida occulta, were detected in 16 of the 23 children (70%). Spinal MRI was normal in 21 patients (91.3%), including 1 with a tethered cord and lipoma associated with a complex skeletal abnormality, and 1 with a nonprogressive, nonsurgical T7 to T9 syrinx. Only the case of lipoma required neurosurgical intervention.

CONCLUSIONS

The value of MRI is limited in children with voiding dysfunction and a normal neuro-orthopedic assessment. This study should be reserved for patients with associated neuroorthopedic findings or complex skeletal deformity on plain x-ray.

Bladder function before and after selective dorsal rhizotomy in children with cerebral palsy

PURPOSE

Approximately a third of children with cerebral palsy are expected to present with dysfunctional voiding symptoms. Selective dorsal rhizotomy, which is indicated for managing lower extremity spasticity in children with cerebral palsy, also has the potential of affecting bladder function. We evaluate the impact of selective dorsal rhizotomy on bladder function by comparing preoperative and postoperative symptoms, and urodynamic parameters in children undergoing selective dorsal rhizotomy for spasticity.

MATERIALS AND METHODS

We reviewed urodynamic studies in 25 boys and 15 girls with a mean age plus or minus standard deviation of 5.43+/-2.1 years who underwent selective dorsal rhizotomy for spasticity at our institution between January 1992 and September 1995. Urodynamics were performed preoperatively only in 22 patients, preoperative and postoperatively in 13, and postoperatively only in 5. Preoperative urodynamic studies were done within 2 weeks of surgery and postoperative studies were done at least 6 months after surgery (mean 1.32+/-0.65 years).

RESULTS

Of the 35 patients with preoperative urodynamic studies total bladder capacity, pressure specific volumes and full resting pressure were abnormal for age in 23 (65.7%). In addition, 17 of the 23 children (74%) were completely asymptomatic. In the group that underwent preoperative and postoperative urodynamic studies there was significant improvement in total bladder capacity (p <0.005) and pressure specific volumes (p <0.005) using the paired Student t test. All children had neurological improvement postoperatively, 5 of 7 (71%) who were incontinent preoperatively became continent and none had deterioration on urodynamics.

CONCLUSIONS

At least half of the children with spastic cerebral palsy have clinically silent bladder dysfunction. Selective dorsal rhizotomy improves spasticity and significantly improves bladder storage characteristics. We propose that urodynamic studies be included in the evaluation of children with spastic cerebral palsy who are possible candidates for selective dorsal rhizotomy to treat lower limb spasticity.

Magnetic resonance imaging in children with voiding dysfunction: is it indicated?

PURPOSE

We evaluated the role of magnetic resonance imaging (MRI) of the lumbosacral spinal cord in children with complicated voiding dysfunction and normal neuro-orthopedic examination.

MATERIALS AND METHODS

We reviewed the records of 32 consecutive children with complicated enuresis who were referred for neurosurgical evaluation, including those with a history of refractory voiding dysfunction or incontinence associated with persistent vesicoureteral reflux, encopresis, or associated leg or back pain. Nine patients were excluded from study because of urethral or anorectal anomalies, or failure to meet the inclusion criteria. Eligible for study inclusion were 23 children with a mean age of 8.9 years. Complete neurological and orthopedic examinations were normal in all patients except 1 with mild scoliosis and 1 with congenital facial palsy.

RESULTS

Urodynamic studies revealed instability in 14 cases, hypertonia in 7, hyporeflexia in 2 and detrusor-sphincter dyssynergia in 4. Skeletal abnormalities, mostly spina bifida occulta, were detected in 16 of the 23 children (70%). Spinal MRI was normal in 21 patients (91.3%), including 1 with a tethered cord and lipoma associated with a complex skeletal abnormality, and 1 with a nonprogressive, nonsurgical T7 to T9 syrinx. Only the case of lipoma required neurosurgical intervention.

CONCLUSIONS

The value of MRI is limited in children with voiding dysfunction and a normal neuro-orthopedic assessment. This study should be reserved for patients with associated neuroorthopedic findings or complex skeletal deformity on plain x-ray.

Low-grade astrocytomas in children: evolving management strategies

Developments in imaging and in neurosurgical techniques over the past decade have substantially altered the management of children with low-grade astrocytoma. Indications for surgery have become more clearly defined, and a larger proportion of children undergo complete or subtotal resection than in the past. Fewer receive adjuvant therapy, even though the options in this regard are more numerous now and theoretically likely to result in less morbidity than conventional external beam radiotherapy. This review will address in particular the correlations between location, imaging appearance, and behavior that need to be more widely appreciated, and present recommendations regarding the management of these tumors.

Continuous unilateral epileptiform discharge and language delay: effect of functional hemispherectomy on language acquisition

PURPOSE

To assess the efficacy of functional hemispherectomy in promoting language acquisition in a child with severe language delay and continuous left hemispheric epileptiform discharge in the absence of clinical seizures. We report a 6-month-old girl who initially presented with a right hemiparesis secondary to a lesion of probable prenatal origin in the distribution of the left middle cerebral artery. Weeks later, she developed infantile spasms. At 1.5 years of age, because of intractable seizures, the patient had fenestration of the left porencephalic cyst and anterior temporal lobectomy. The seizures ceased; however, language development remained limited to 35 words at 3.5 years of age. The EEG showed almost continuous epileptiform activity over the left hemisphere with no independent epileptiform potentials contralaterally. She underwent a functional left hemispherectomy.

METHODS

Imaging, electroencephalographic investigation, pre- and postoperative psychological and speech assessment were carried out.

RESULTS

Considerable language, speech, and behavior improvement was noted within 2 months of surgery.

CONCLUSIONS

Interictal epileptiform discharges can interfere with the development of contralateral hemispheric function in the absence of clinical seizures. Early functional hemispherectomy may have a role in promoting optimal language development in appropriately selected patients. Although the primary indication for functional hemispherectomy is to control intractable seizures, a secondary proposed indication is to reduce functional impairment of the other hemisphere by electrical interference.

Pediatric brain stem gliomas: a review

Tumors arising in the brain stem, comprising the midbrain, pons, and medulla oblongata, are now recognized as distinct clinico-pathological entities. Advances in neurosurgical techniques have made surgery not only feasible but the treatment of choice for some of these tumor types. Previously the mainstay of treatment, radiotherapy is now used more selectively. This article reviews the current state of knowledge with regard to tumors arising in the brain stem, the therapeutic options available for each, and provides recommendations with regard to management.

Use of the prone position in the MRI evaluation of spinal cord retethering

In order to determine the impact of magnetic resonance imaging (MRI) in the management of spinal cord retethering, we retrospectively reviewed case and imaging records of 51 patients who underwent MRI examination in supine and prone positions. Group 1 included 8 control patients without cord tethering. They exhibited a normal level of the conus medullaris with normal surrounding subarachnoid space, and consistent anterior migration of the conus within the dural sac on MRI in prone position. Group 2 included 17 patients with tethered cord secondary to occult spinal dysraphism (spinal cord lipoma in 6 patients, thick filum terminale in 4, diastematomyelia in 4, myelomeningocele manqué in 2, and dermoid tumour in 1). Supine and prone MRI performed at a median period of time of 6 months after untethering showed resolution of posterior tethering in 5 out of the 7 patients who exhibited pre-operatively dorsal attachment of the spinal cord to the dura. Anterior migration of the conus or of the cord/filum complex in prone position was observed in only 24% of the cases. Group 3 included 26 patients with secondary tethered cord following prior myelomeningocele closure. Their MRI performed at a median interval of time of 11 months following untethering demonstrated resolution of the posterior cord tethering in only 8 out of the 24 patients who exhibited this feature pre-operatively. Anterior migration within the expanded dural sac was never noted in this group. We conclude that spine MRI is of limited value and that prone-positioned MRI is of no additional use in the evaluation of spinal cord retethering.

Traumatic aneurysm from shaken baby syndrome: case report

OBJECTIVE AND IMPORTANCE

We present a 6-week-old infant who developed a traumatic aneurysm from clearly documented shaken baby syndrome. Despite the theoretical similarity in the mechanism of such injuries, this is the first aneurysm reported that resulted from such a cause. The infant is also the youngest reported patient to have suffered from a traumatic aneurysm.

CLINICAL PRESENTATION

Police records documented shaking of the child as well as direct impact on the child's head. Three weeks later, the patient developed an intracerebral hemorrhage, which was revealed by angiography to have resulted from a pericallosal artery aneurysm.

TECHNIQUE

The aneurysm was totally resected through a porencephalic cyst, which had developed secondary to ischemic injury to the brain.

CONCLUSION

The temporal course, as well as the location of this traumatic aneurysm, is similar to that in older patients.

Impact of urodynamic studies on the surgical management of spinal cord tethering

To determine the usefulness of urodynamic studies in the management of children with a suspected tethered spinal cord, the authors retrospectively reviewed case records of 25 patients evaluated both pre- and postoperatively using this diagnostic adjunct. All patients were also evaluated with magnetic resonance imaging or computerized tomography myelography. Seven patients who presented initially with orthopedic deformity, skin stigmata, and neurological problems underwent primary cord untethering (Group 1). All seven patients were urologically asymptomatic; all but one had normal findings on urodynamic study. Eighteen patients with prior myelomeningocele closure underwent secondary untethering (Group 2). They presented with urological (11 cases), neurological (three cases), or both urological and neurological (four cases) deterioration. All patients underwent surgery via a microsurgical technique. At a mean follow-up time of 2 years, the only Group 1 patient with preoperative abnormal urodynamic findings normalized following untethering, whereas another asymptomatic patient showed worsened results on his postoperative study. In Group 2, all seven patients with preoperative neurological deterioration improved. Ten of the 15 patients who had isolated or associated preoperative clinical urological deterioration improved or stabilized, whereas five displayed continued deterioration in their bladder function. With respect to urodynamic studies, there was a significant increase in total and pressure-specific bladder capacities following untethering. We conclude that urodynamic studies are useful both diagnostically and in follow-up examinations of patients with tethered cord, that disturbances identified by these studies often precede clinical manifestations of deterioration, and that spinal cord untethering favorably influences the urological status in most patients.

Comparison of syringopleural and syringosubarachnoid shunting in the treatment of syringomyelia in children

Case records from the Montreal Children's Hospital containing the diagnosis of shunted syringomyelia were retrospectively reviewed. From 1984 to 1994, 31 patients had their syrinx treated by either syringopleural (19 cases, Group A) or syringosubarachnoid (13 cases, Group B) shunting. One patient was included in both groups. Associated diagnoses included: in Group A, two cases of Chiari I and 14 of Chiari II malformations, 14 cases of shunted hydrocephalus, 13 cases of spina bifida aperta, and three cases of spina bifida occulta; Group B, four cases of Chiari I and two of Chiari II malformations, four cases of shunted hydrocephalus, two cases of spina bifida aperta, and five cases of spina bifida occulta. Eight Group A and six Group B patients had undergone prior posterior fossa decompression. Motor deficits predominated in both groups and arachnoiditis was a uniform operative finding. Neurological follow-up examinations showed 11 Group A patients improved and eight stabilized, whereas on magnetic resonance imaging, 12 cavities appeared to have collapsed, five were markedly reduced, and one had increased. One patient underwent reoperation for pleural effusions and one for shunt displacement. In Group B, one patient improved, eight stabilized, three worsened neurologically, and one was lost to follow-up review. Radiologically, one cavity appeared to have collapsed, six were significantly reduced, two were unchanged, and three had enlarged. The authors conclude that syringopleural shunting is a valuable option for controlling syringomyelia in patients without Chiari malformation or in patients who have previously undergone a craniovertebral decompression or are otherwise asymptomatic from their Chiari malformation.

Encephaloduroarterio-synangiosis in a child with sickle cell anemia and moyamoya disease

We report a black girl with sickle cell anemia. On prophylactic exchange transfusion protocol, she experienced cerebrovascular accidents at 3 and 3.5 years of age, both associated with transient right hemiparesis. At 7.5 years of age, she presented with a partial motor seizure and a left hemiparesis. A cerebral angiogram demonstrated stenosis at the origins of both middle and anterior cerebral arteries bilaterally with extensive basal collateralization. She underwent uncomplicated bilateral encephaloduroarteriosynangiosis (EDAS) procedures using both superficial temporal arteries. At age 9 years, the patient presented with a severe headache and tunnel vision secondary to a stenosis of both posterior cerebral arteries. She underwent bilateral EDAS procedures using both occipital arteries. No complication was encountered. Postoperative cerebral angiogram demonstrated impressive neovascularity at the sites of all four EDAS procedures. Different treatment options of moyamoya disease are discussed.

Cauda equina histiocytosis X

A young child was admitted with a cauda equina syndrome believed to be progressive, but unrelated to a congenital anomaly. Magnetic resonance imaging studies revealed the presence of an intradural tumor in the cauda equina. A yellow pasty tumor with nerve root infiltration was identified at surgery. Histologic features were pathognomonic for histiocytosis X. The patient's management and review of the literature are discussed.

Radionuclide shuntogram: adjunct to manage hydrocephalic patients

We reviewed our experience with shuntograms to establish technical criteria that would optimize the reliability of this test in managing patients with shunt malfunction.

METHODS

Fifty-six shuntograms were performed in 47 children presenting with symptoms of shunt malfunction not elucidated by conventional radiological examination. Shuntograms were performed by injecting 0.5 ml 99mTc-DTPA in the reservoir of the shunt.

RESULTS

There were 22 shuntograms in which ventricular reflux occurred and the entire shunt system was visualized. At surgery, three patients in this group presented partial obstruction of the ventricular and/or peritoneal catheter. A second group of patients had 15 shuntograms that showed normal proximal reflux but abnormal distal drainage. Ten patients in this group presented distal obstruction or fracture, valve dysfunction or peritoneal adhesions at surgery. A third group of patients with 19 shuntograms exhibited no proximal reflux. At surgery, twelve had an obstructed ventricular catheter and the last case showed overdrainage. Symptoms of nonsurgical patients abated spontaneously.

CONCLUSION

The shuntogram is a useful procedure in the management of patients presenting with shunt-related problems. For consideration as a normal result, a shuntogram must exhibit ventricular reflux, the shunt system must be entirely visualized and the isotope must diffuse uniformly in the peritoneal cavity. Whereas rapid radionuclide clearance is a useful parameter in eliminating a distal obstruction. It is a misleading sign for proximal blockage. Absence of ventricular reflux is highly suggestive of proximal reflux. Implicit to this conclusion is the fact that the presence of a reservoir proximal to the valve greatly facilitates the performance and interpretation of a shuntogram.

Supratentorial ectopic ependymoma

BACKGROUND

Ependymomas usually arise from the ventricular surface.

METHODS

We report an 11-year-old female who presented with a supratentorial ectopic ependymoma.

RESULTS

The patient presented with a two-month-history of progressive headache, nausea and vomiting. Examination revealed papilledema, horizontal nystagmus, diplopia on upward gaze, and right pronator drift. CT scan showed an enhancing left precentral subcortical lesion measuring 3 cm in diameter with associated edema and mass effect. Its medial border was located 3 cm from the ependymal surface of the ventricle. A firm tumour was dissected from the centrum semiovale white matter, and removed in toto as confirmed on MRI. Pathological examination revealed histological, immuno-histochemical and electron microscopic features consistent with an ependymoma. Spine MRI and bone marrow aspirate, as well as lumbar puncture of cytology failed to show any dissemination.

CONCLUSION

From the literature review, this represents an exceptional ependymoma located at the distance from the ventricular system or cisterns. Different pathogenic alternatives are discussed.

Negative-pressure hydrocephalus

Two cases of children with closed myelodysplasia, Arnold-Chiari malformation, and shunted hydrocephalus who underwent spinal arachnoid cystopleural shunting are presented. Postoperatively, both patients developed craniovertebral symptomatology accompanied by radiologically documented ventricular dilation in spite of negative intracranial pressure and functional ventriculoperitoneal (VP) shunts. Both patients recovered after the cystopleural shunts were revised to increase the resistance to flow within the system. The authors believe that some communication between the arachnoid cyst and the subarachnoid space existed in both cases and that the negative pleural pressure was transmitted preferentially to the spinal and cerebral convexity subarachnoid spaces with relative sparing of the ventricular system. A transmantle pressure gradient was thereby established, leading to ventricular dilation. The authors further suggest that a craniospinal gradient was possibly established as well, leading to craniovertebral symptomatology in the patients. Return of flow in the VP shunts was obtained by correcting this iatrogenic transmantle pressure gradient.

Masson's vegetant haemangio-endothelioma

We present a 14-year-old patient who had a scalp mass that enlarged on dependent positioning. This mass was located in the surgical bed of a previously excised scalp lesion. Valsalva manoeuvre assisted computerized tomography demonstrated this lesion to enhance with contrast and to vary in size. At surgery, a bluish firm mass, located in the galea of the left frontal region, was resected. Total removal resulted in no recurrence at 18 months. Pathological examination revealed a vascular tumour that was first described by Pierre Masson. This is characterized by intravascular vegetations composed of cells of endothelial origin. The exact pathogenesis of these lesions is unknown, but the prognosis based on the review of the literature is expected to be good.

Lesionectomy of MRI detected lesions in children with epilepsy

The results of complete excision of cerebral lesions detected by MRI in 18 children presenting with epilepsy were analyzed. There were 14 boys and 4 girls with a mean age of 9.2 years. The average age of onset of seizures was 6.8 years. The mean time from onset of seizures to surgery was 2.3 years. Often, CT scans suggested that the lesions were indolent. MRI was better in differentiating neoplastic from developmental lesions. Angiography was non-contributory in this series. Interictal EEGs showed epileptiform activity correlating with imaging studies in 54% of children. The lesion was completely surgically excised in all patients. This was confirmed by intra-operative ultrasound and postoperative imaging. Electrocorticography was performed prior to and after the resection, but residual spiking did not lead to further resection. The average postoperative follow-up was 5.7 years. Five patients had low grade astrocytomas, 4 had gangliogliomas, 1 a mixed astrocytoma-oligodendroglioma, 3 had cortical dysplasia, 2 infantile desmoplastic gangliogliomas, 2 hamartomata, and 1 cavernous angioma. Sixteen patients have been seizure-free since surgery. Only 2 have partial seizures. Thus, all patients benefited from the resection, with respect to seizure control. In those with temporal lobe lesions, improvement in IQ was seen postoperatively. Early consideration of surgery in patients with epilepsy and lesions demonstrated by MRI is suggested.

Encephaloduroarteriosynangiosis (EDAS) for the treatment of childhood moyamoya disease

Moyamoya disease is defined by the angiographic demonstration of stenosis or occlusion of the vessels of the anterior circulation at the base of the brain and the concomitant development of collateral blood supply. Untreated, the disease is often clinically progressive, resulting in significant neurologic sequelae. Encephaloduroarteriosynangiosis (EDAS), which involves the transposition of a segment of a scalp artery onto the surface of the brain, is a surgical treatment aimed at improving collateral blood flow. Six children underwent 8 EDAS procedures and were followed from 6 months to 9 years after surgery. No patient experienced further deterioration in neurologic status. Postoperative angiography demonstrated cerebral revascularization from the donor scalp artery on 3 of the 6 EDASs that were studied. The 2 patients who did not revascularize after EDAS demonstrated angiographic regression of their disease. The data suggest that EDAS is a safe procedure for the treatment of childhood moyamoya disease. Given the potential severity of the sequelae, early operative intervention is recommended in all children with this disease.

Stereotactic transtentorial hiatus ventriculoperitoneal shunting for the sequestered fourth ventricle. Technical note

The authors describe a technique of stereotactic transtentorial hiatus ventriculoperitoneal shunting for the treatment of the sequestered fourth ventricle, used successfully in the care of four patients. They recommend it as a safe, effective treatment of patients suffering from an isolated fourth ventricle.

Newborn apnea caused by a neurofibroma at the craniocervical junction

The authors report, for the first time, the finding by magnetic resonance imaging of a neurofibroma at the craniocervical junction with upper cervical cord and lower brainstem compression causing complete apnea from birth. Subsequent subtotal resection of the neurofibroma resulted in the successful extubation of a previously ventilator-dependent patient. After a two month period of breathing spontaneously, the newborn developed an upper respiratory tract infection and was reintubated. The patient, unable to be weaned off of the respirator, was extubated and expired shortly thereafter, at the age of five months. The authors suggest that in newborns with unexplained apnea, MRI of the cranio-cervical junction is indicated. Certain patients may be discovered who have less compromised cervico-medullary function and are afflicted by less aggressive forms of neurofibromatosis type 1. These patients may benefit permanently from a surgical decompression.

Stereotactic external beam irradiation in previously untreated brain tumors in children and adolescents

Stereotactically guided external beam irradiation may be a useful form of treatment for small, well-circumscribed, but surgically inaccessible, primary brain tumors that are either benign or of low malignant potential. Between March 1988 and December 1991, 10 children and adolescents with previously untreated primary brain tumors were treated with stereotactic external beam irradiation (SEBI) using a linac-based dynamic technique. Eleven lesions were treated in the 10 patients. Treatment was given using a collimator diameter of 1.5-4 cm (median 2 cm). Single fractions of 18, 20, and 25 Gy were used for 3 lesions in 2 patients. A fractionated schedule delivering a median dose of 42 Gy in 6 fractions over 2 weeks was used in the remaining 8 patients. Morbidity related to treatment was minimal. Three patients suffered a temporary worsening of preexisting neurological symptoms and/or signs at 2, 5, and 5 months posttreatment, with subsequent recovery in all. With a median follow up post-SEBI of 17.5 months (range 5-47 months), improvement in neurological findings related to the lesion was noted for 5 treated lesions; 6 remained clinically stable. Seven of the 11 treated lesions improved radiologically, and only 2 showed evidence of progressive disease. Stereotactic external beam irradiation represents a potentially valuable therapeutic option for selected primary brain tumors in the pediatric and adolescent age group. Morbidity related to the treatment appears acceptable in frequency and type, and preliminary data with regard to response are encouraging. However, in order to assess the impact of such treatment on long-term tumor control and survival, further experience with a larger cohort of patients followed for a longer period of time will be necessary.

Ganglioglioma presenting as a vascular lesion in a 10-year-old boy. Case report

The authors present the case of a 10-year-old boy admitted for evaluation of a generalized seizure and a history of headaches. Computerized tomography (CT) and gadolinium-enhanced magnetic resonance (MR) imaging demonstrated a large nonhomogeneous contrast-enhancing mass of the left frontal lobe, with a large cystic component. Cerebral angiography revealed the lesion to be highly vascular and fed entirely by the internal carotid artery system. The patient underwent craniotomy and the lesion was completely removed. Neuropathological study revealed that the tumor was a ganglioglioma. On review of the literature, it was found that gangliogliomas often present in the second and third decade, are known to have cystic components, and are contrast-enhancing on CT and MR imaging; however, they are classically known to be avascular on angiography. This case of a markedly vascular ganglioglioma emphasizes that these tumors should be included in the differential diagnosis of vascular supratentorial lesions.

Adult intramedullary spinal cord ependymomas: the result of surgery in 38 patients

Thirty-eight patients underwent surgery for an intramedullary spinal cord ependymoma. In 37 patients, postoperative magnetic resonance imaging confirmed that the tumor was totally removed. The morbidity of surgery was directly related to the preoperative neurological condition. Patients who were normal or nearly normal preoperatively were rarely worse after surgery, and those who had significant disability preoperatively were at greatest risk of being more impaired after surgery. There has been no tumor recurrence in any patient after a mean follow-up period of 24 months, and radiation therapy has not been employed as a surgical adjunct.

Brain-stem glioma growth patterns

During the last decade, several authors have reported that certain brain-stem gliomas may be associated with a better prognosis than others. In this paper, retrospective correlations between the pathological findings and the magnetic resonance (MR) imaging appearance of 88 brain-stem gliomas are established. The authors propose an anatomical hypothesis that helps identify glioma growth patterns in general and that clarifies why cervicomedullary, dorsally exophytic, and focal tumors have a more favorable prognosis. According to this hypothesis, growth of benign gliomas of the brain stem is guided by secondary structures such as the pia, fiber tracts, and the ependyma, which in turn leads to stereotypical growth patterns that are clearly identified on MR images. The authors believe that this hypothesis, in conjunction with clinical data, may help establish selection criteria for the surgical treatment of specific brain-stem lesions.

Adult intramedullary astrocytomas of the spinal cord

In this series, 25 adult patients with intramedullary astrocytomas were treated by radical excision alone. Six patients proved to have anaplastic astrocytoma; five of them died within approximately 2 years and the sixth has demonstrated disease progression. The other 19 patients were diagnosed as having low-grade astrocytoma (16 cases) or ganglioglioma (three cases); two of these had advanced preoperative neurological disability and died of medical complications. Fifteen of the remaining 17 patients have no clinical evidence of tumor recurrence after a mean follow-up period of 50.2 months; the other two have a small residual neoplasm that demonstrates no progression. Of these 17 patients, seven had previously received radiation therapy, but had clear evidence of tumor growth subsequently. This experience suggests that surgery is not beneficial for anaplastic spinal astrocytoma. However, in cases of low-grade tumor, radical excision is associated with minimal morbidity and an excellent long-term prognosis when carried out before significant disability occurs.

Intraventricular central neurocytoma

A case of central neurocytoma treated surgically is described. The authors review the literature. Emphasis is placed on radiological and pathological features not previously described. In particular, the intra-operative ultrasound appearance is described. The role of adjunctive radiotherapy is also discussed.

Otitis media and CNS complications

Intracranial complications from otitis media can be quite devastating to the patient if an early diagnosis is not made. Patients may develop meningitis, venous sinus thrombosis or cranial nerve palsies, as well as intracranial abscess. The presenting features in such cases may be subtle and include headache, nausea, vomiting, personality changes and signs of increased intracranial pressure as well as focal neurological deficits. A case of intracranial brain abscess is presented in a patient with a history of chronic otitis media with cholesteatoma. Delay in the diagnosis of intracranial complications of otitis media can lead to improper treatment with increased morbidity and mortality. The etiology and treatment of complications affecting the CNS is discussed.

Intraoperative ultrasonography: an important surgical adjunct for intramedullary tumors

The echographic characteristics of 186 suspected intramedullary spinal cord tumors were reviewed. Ultrasonography was found to be specific in distinguishing the tumor type, the extent of the lesion, and the presence and type of associated cysts. Ultrasonography greatly facilitates the selection of respective sites for the placement of a myelotomy, and for initiation of the resection. Additionally, this indispensable adjunct provides ongoing images that allow the preoperative plan to be precisely followed in a surgical field where anatomical landmarks are limited and the margin for error is minimal.

Trends in surgery: laser surgery, use of the cavitron, and debulking surgery

The purpose of this article is to expose nonneurosurgeons to high-level technological adjuncts used by pediatric neurosurgeons for the treatment of pediatric central nervous system disease. Some of the characteristics of the instruments and their most important uses are described. Emphasis is placed on the impact this technology has had in the development of "new" operations. Surgical limitations and future perspectives are also discussed.

Pediatric spinal cord tumor surgery

This article discusses our experience in managing pediatric spinal cord tumors. A description of the clinical presentation of children with such lesions and of the radiological characteristics of these tumors is given. Emphasis is placed on treatment philosophy and objectives as well as on surgical technique. Our results and the complications in treating 95 children with spinal cord tumors are outlined.

Characterization of lymphoid cells isolated from human gliomas

To analyze the phenotypic profile of lymphoid cells freshly isolated from surgically resected human gliomas, a double-immunostaining technique was developed which permitted the investigators simultaneously to distinguish between hematogenous and tumor cell populations and to detect expression of lymphocyte-monocyte subset-specific antigens on hematogenous cells. With this technique, the profiles of tumor-infiltrating lymphocytes (TIL's) derived from high- and low-grade gliomas were compared with phenotypes of lymphocytes concurrently isolated from peripheral blood. The total leukocyte cell yield from high-grade glioma cases exceeded that of low-grade cases. In nine high-grade glioma cases the proportion of CD8-positive cells was increased within the TIL population (41.2% +/- 1.9%, mean +/- standard error of the mean) as compared to the corresponding peripheral blood lymphocyte (PBL) population (30.8% +/- 4.1%, p less than 0.05). The proportion of natural killer HNK-positive cells, some of which bear the CD8 antigen (although not necessarily the pan T cell antigens CD2 and CD3), was also increased in the TIL's (41.9% +/- 4.2%) compared to that found in PBL's (32.1 +/- 5.6%, p less than 0.05) of high-grade glioma cases. The observed phenotypic pattern of high-grade glioma TIL's is similar to that reported based on immunohistochemical analysis of tumor tissue sections, suggesting that the techniques described here resulted in isolation of lymphoid cells representative of TIL's.

Intracerebral cavernous angiomas

We studied 31 patients with histologically verified intracerebral cavernous angiomas. Twenty-two patients were symptomatic; nine were asymptomatic. All 22 symptomatic patients had seizures, three had intracranial hemorrhage, and one had signs of a space-occupying lesion. Twenty-seven lesions were located in the neocortex, three in the brainstem, and one in the cerebellum; all exhibited characteristic gross and microscopic features of cavernous angiomas. CT identified the location and extent of the lesion in 16 of 27 cases. Six of seven lesions demonstrated contrast enhancement, and ten of 27 scans harbored densities consistent with intracerebral calcium. Angiography was performed in 17 cases and was completely normal in eight. MRI revealed mixed signal intensity centrally with a ring of decreased signal intensity peripherally on T2-weighted images and was diagnostic in five cases. Surgical treatment offers an excellent prognosis for seizure control in patients with such lesions.

Neurocysticercosis: surgical and medical management with praziquantel

Eight cases of neurocysticercosis were encountered at the two major neurological centers affiliated with McGill University in Montreal in 4 years. All patients were immigrants who had been in Canada for a period of 1 to 18 years and came from South America (three cases), Haiti (three cases), and Greece (two cases). Five patients had parenchymal cysts and presented with epilepsy; three had the racemose form and presented with hydrocephalus. Four patients with parenchymal cysts were treated by removal of the cysticercus and did well. One patient with numerous cysts was treated with praziquantel with good clinical and radiological results. Two patients with the racemose form were treated by cyst aspiration, cerebrospinal fluid (CSF) diversion, and praziquantel and did well. Another patient with the racemose form, seen before the advent of praziquantel, died of cysticercosis infection. Neurocysticercosis is not uncommon in the immigrant population of large North American cities. Single symptomatic cysts can be evacuated surgically with good results; multiple parenchymatous cysts can be treated with praziquantel. Patients with the racemose form who are treated with CSF diversion and praziquantel do well, although those who are only treated surgically die of their disease.