Diffusion tensor imaging characteristics of the corpus callosum in mild, moderate, and severe traumatic brain injury

BACKGROUND AND PURPOSE

The corpus callosum is an important predilection site for traumatic axonal injury but may be unevenly affected in head trauma. We hypothesized that there were local differences in axonal injury within the corpus callosum as investigated with diffusion tensor imaging (DTI), varying among patients with differing severity of traumatic brain injury (TBI).

MATERIALS AND METHODS

Ethics committee approval and informed consent were obtained. Ten control subjects (7 men, 3 women; mean age, 37 +/- 9 years) and 39 patients with TBI (27 men, 12 women; 34 +/- 12 years) were investigated, of whom 24 had mild; 9, moderate; and 6, severe TBI. Regions of interest were selected in the callosal genu, body, and splenium to calculate fractional anisotropy (FA), apparent diffusion coefficient (ADC), and the number of fibers passing through. Statistical comparison was made through analysis of variance with the Scheffé post hoc analysis.

RESULTS

Compared with controls, patients with mild TBI investigated <3 months posttrauma (n = 12) had reduced FA (P < .01) and increased ADC (P < .05) in the genu, whereas patients with mild TBI investigated > or =3 months posttrauma (n = 12) showed no significant differences. Patients with moderate and severe TBI, all investigated <3 months posttrauma, had reduced FA (P < .001) and increased ADC (P < .01) in the genu compared with controls and reduced FA in the splenium (P < .001) without significant ADC change.

CONCLUSION

Mild TBI is associated with DTI abnormalities in the genu <3 months posttrauma. In more severe TBI, both the genu and splenium are affected. DTI suggests a larger contribution of vasogenic edema in the genu than in the splenium in TBI.

Diaphragm recovery by laryngeal innervation after bilateral phrenicotomy or complete C2 spinal section in rats

This study aimed to highlight the functional aspects of diaphragm reinnervation by laryngeal motoneurons after bilateral phrenicotomy or complete cervical transection. The left recurrent laryngeal nerve was connected to the left phrenic nerve in 14 rats. Five months later, all bridged rats presented a substantial ipsilateral diaphragm recovery (74.2 +/- 10% of contralateral activity) whereas the diaphragm remained paralysed in non-bridged rats (n = 5/5). After additional right phrenicotomy, functional breathing persisted in bridged rats whereas all non-bridged died. After complete C2 spinal transection, diaphragm respiratory discharges persisted in bridged rats. The reinnnervation by laryngeal motoneurons was confirmed by retrograde labeling, stimulus-elicited diaphragm response by vagal stimulation and diaphragm inactivation after vagotomy. In conclusion, the recurrent-phrenic nerve anastomosis induces a reliable functional diaphragm outcome even after contralateral diaphragm denervation or complete high cervical spinal cord injury, and could be considered as a clinical repair strategy for re-establishing diaphragm autonomy following spinal cord trauma.

Biopsie endoscopique diagnostique d’un cas de neurosarcoïdose

A 56-year-old woman was followed in the neurological department for febrile mental confusion. The diagnosis of sarcoidosis was suggested on the ground of associated abdominal lymphadenopathy, elevated serum angiotensin-converting enzyme level, aseptic meningitis and intracranial hypothalamic lesion. Nevertheless, radiological, biological and histological analyses could not assert the diagnosis of systemic sarcoidosis. Six months later, cerebral MRI showed a recent enhanced nodule, located near the right choroid plexus, inducing a dilatation of the right temporal ventricular horn. A surgical endoscope-assisted biopsy of that lesion was decided. The endoscope was introduced in the right trapped temporal ventricle. The limits between normal and pathological tissues were clearly identified. The biopsy was thus accurately performed. Histological analysis definitely confirmed the diagnosis of neurosarcoidosis. No postoperative complication was noted. We report a case of neurosarcoidosis which was diagnosed by ventricular endoscope-assisted biopsy. The discussion stresses the potential advantages of endoscopy for the diagnosis of small periventricular lesions when ventricular dilatation is associated.

A new model of upper cervical spinal contusion inducing a persistent unilateral diaphragmatic deficit in the adult rat

Research on spinal cord trauma requires models reflecting the contusion mechanisms encountered in clinical situation. The aim of this study was to develop in the adult rat a reproducible model of upper cervical spinal cord contusion inducing persistent unilateral diaphragm deficit. After dura and pia matter removal, weight drop and compression were targeted at the ventro-lateral funiculi which contain the bulbospinal descending respiratory pathways that command the phrenic motoneurons innervating the diaphragm. At 7 days post-injury, the left diaphragm activity recorded in contused rats (27.4 +/- 5.1% of the contralateral activity) was significantly lower than in the sham group (97.6 +/- 1.2%). This respiratory deficit still persisted 1 month later. Histology showed a reproducible left C2-lateralized lesion that involved both white and gray matter including the ventro-lateral funiculi. This C2 contusion model provides a basis for testing both regenerative and neuroprotective strategies aimed at improving functional respiratory recovery after spinal cord trauma.

MR diffusion tensor imaging and fiber tracking in 5 spinal cord astrocytomas

Spinal cord astrocytomas are rare neoplasms that can result in alteration of the spinal cord structural integrity, which can be assessed by using diffusion tensor imaging methods. Our objective was to visualize the deformation of the posterior spinal cord lemniscal and corticospinal tracts in 5 patients with low-grade astrocytomas compared with 10 healthy volunteers by using 3D fiber-tracking reconstructions.

Endoscopie et traitement chirurgical des macroadénomes hypophysaires endo- et suprasellaires invasifs

BACKGROUND AND PURPOSE

Surgery of invasive endo- and suprasellar pituitary macroadenomas remains difficult. The records of 13 consecutive patients who underwent transsphenoidal surgery were analyzed in order to evaluate advantages and limitations of endoscopy for surgery of invasive pituitary macroadenomas.

METHODS

A transseptal transsphenoidal intersepto-columellar approach was performed with a nasal 0-degree endoscope. Removal of the macroadenoma was performed under the control of a microscope. When the tumor seemed to be completely removed with microscope, a rigid 30-degree endoscope was inserted in the intrasellar and suprasellar regions in order to detect residual adenoma tissue. These residues were removed when technically possible.

RESULTS

No rhinologic complication was noted. In 7 patients, the intra- and suprasellar endoscopic view detected a tumor residue which could be removed in each case. Two cases of cerebrospinal fluid leakage occurred during the complementary tumor resection. Two cases of diabetes insipidus and two of rhinorrhea were reported postoperatively. The analysis of the postoperative MRIs showed a complete removal in 23% of the patients (3/13), 75 to 100% removal in 54% of the patients (7/13), 50 to 75% removal in 8% of the patients (1/13) and 50% removal in 15% of the patients (2/13). More than 75% removal was thus achieved in 77% of the patients (10/13). The mean follow-up was 27.2 months.

CONCLUSIONS

Rhinologic morbidity was reduced with the endoscopic endonasal approach. Endoscopy complemented with a microscope offered an optimal view of the intra- and suprasellar regions. Endoscopy also improved tumor resection of the invasive endo- and suprasellar pituitary macroadenomas by visualizing hidden suprasellar tumor residues. However, endoscopy was associated with a higher rate of postoperative rhinorrhea.

Multiple lumbar plexus neurotizations of the ninth, tenth, and eleventh intercostal nerves

The topographic anatomy of the lower intercostal nerves is less known than the upper ones except for the twelfth intercostal nerve. It is possible to use the lower intercostal nerves to carry out a neurotization of the lumbar roots. We studied the anatomy of the ninth, tenth, and eleventh intercostal nerves in order to specify the data of descriptive and topographic anatomy allowing to carry out their harvesting under good conditions. Ninth, tenth, and eleventh intercostal nerves of 50 cadavers were dissected. The proximal part of the nerve in the posterior intercostal space was exposed through a posterior approach. The lateral intercostal space was exposed through a lateral approach, under the latissimus dorsi, which made it possible to harvest the intercostals nerve. The proximal course of the nerve in posterior intercostals space was the same in all the cases. The nerve moves obliquely towards the outside to reach the lower border of the rib. The exit of posterior intercostal space is a fibrous strait that marks the entry of a channel between two muscular layers. We describe an aponevrotic channel in which the nerve and the vessels are, immediately at the lower border of the cranial rib. The mean total length of intercostal nerve harvested by our technique was 17.96 cm for the ninth intercostal nerve, 17.14 cm for the tenth intercostal nerve, and 15.94 cm for the eleventh intercostal nerve. The bifurcation of the intercostal nerve in a deep branch and the ramus cutaneus lateralis was found in the majority of the cases, from 9.5 to 21 cm of the emergence of the intercostal nerve in posterior intercostal space. This anatomical study of the ninth, tenth, and eleventh intercostal nerves in posterior intercostal space and lateral intercostal space appears to us to allow the realization of a reliable surgical harvesting.

Cross-neurotization of the caudal brachial plexus with the contralateral C-8 ventral nerve branch in the cat. Potential surgical applications, effects of graft collection on the healthy donor limb and results

Contralateral transfer of the right, eighth ventral nerve branch (C8) (C8 cross-transfer - C8CT) was performed in 6 adult cats, in which the caudal part of the left brachial plexus (C8 and T1) had been severed, in order to mimic nerve root avulsion. Clinical and electrophysiological parameters, muscle contraction force measurements and histology were used to evaluate the effects of the surgery in a 14- to 36-month follow-up. The right forelimb (donor side) was clinically normal (no lameness) in all the cats at the end of the study. Electromyography performed 14 days after surgery revealed denervation fibrillation potentials in both forelimbs. Fibrillation potentials disappeared in all the cats at the end of the study. Direct stimulation of the right C8 ventral branch induced motor and sensory evoked potentials in the left limb muscles in all the cats. The left to right contraction ratio of the extensor carpi radialis muscle was approximately 1. This experimental study demonstrates that C8CT enables re-innervation of the contralateral brachial plexus and allows the establishment of new functional neuromuscular units. This can in turn enable the restoration of function, and could potentially lead to partial recovery after caudal brachial plexus avulsion in the cat.

Clampage vasculaire temporaire

In many situations, temporary artery occlusion is an integral component of aneurysm surgery. The use of temporary clip may allow safer and easier aneurysmal dissection and clipping. Several points, concerning the duration and overall risks of temporary occlusion and the method of choice for cerebral function monitoring have to be discussed.

MATERIAL AND METHODS

Non exhaustive review of neurosurgical literature.

DISCUSSION

Temporary clip application decreases the risk of intraoperative aneurysmal rupture. The analysis of data published in the literature showed that several questions remain open concerning the optimal method of neuroprotection and cerebral function monitoring, as well as the limit of occlusion duration. Other clinical trials are needed to assess the efficacy and safety of this technique.

Experimental bypass surgery between the spinal cord and caudal nerve roots for spinal cord injuries

Spinal cord injuries often cause permanent neurological deficits and are still considered as inaccessible to efficient therapy. Injured spinal cord axons are unable to spontaneously regenerate in adult mammalians. Re-establishing functional activity especially in the lower limbs by reinnervating the caudal infra-lesional territories could represent an attractive therapeutic strategy. For several years, we have studied and developed surgical bypasses using peripheral nerve grafts bridging the supra-lesional rostral spinal cord to the caudal infra-lesional lumbar roots. Main objectives were: 1- to overcome the spinal cord lesion and the consecutive glial barrier blocking the axonal regeneration; 2- to find and bring an alternative source of regenerating axons; 3- to guide those axons toward precisely definite targets (for example, lower limb muscles). We report here the results of our experimental research, which led us from animal experimental models (rodents, primates) to the first human experimentation. Limitations of the method (especially technical pitfalls) are numerous. However, we have obtained encouraging results in our attempts to "repair" the motor pathway. Functional recovery with strong evidence of centrifugal axonal regeneration from the spinal cord to the periphery has been observed. Regarding the sensory pathway, we have found evidence of centripetal axonal regeneration from the periphery toward the spinal cord. Further studies are obviously advocated, but our experimental model of spinal cord - nerve roots bypasses may be integrated in future "repair" strategies of both motor and sensory pathways following spinal cord injury.

Late spinal dislocation after treatment of spinal arteriovenous malformation

Neuropathic arthropathy of the spine is a destructive condition of the spine which is secondary to a loss of the protective proprioceptive reflexes. In the majority of cases, it occurs in patients who have suffered from traumatic medullary lesions and is responsible for destruction of the vertebral bodies and considerable spinal deformity. We report a case of neurogenic lumbar arthropathy in a patient with a spinal arteriovenous malformation. This vascular lesion caused considerable disturbances of proprioception. The course was favorable with regard to the deformity after correction and fusion by posterior approach.

The thoracoabdominal intercostal nerves: an anatomical study for their use in neurotization

The topographic anatomy of the lower intercostal nerves is less known than that of the upper ones, except for the subcostal nerve (twelfth intercostal nerve). It is possible to use the lower intercostal nerves to neurotize the lumbar roots. We studied the anatomy of the ninth, tenth and eleventh intercostal nerves in order to specify the descriptive and topographical anatomical data that will allow their harvest in good condition. The ninth, tenth and eleventh intercostal nerves of 30 cadavers were dissected. The proximal part of the nerves in the posterior intercostal space was exposed through a posterior approach. The lateral intercostal space was exposed through a lateral approach, deep to the latissimus dorsi, that made it possible to harvest the intercostal nerve. The proximal course of the nerves in the posterior intercostal space was the same in all cases. The nerves move obliquely towards the outside to reach the lower border of the rib. The exit of the posterior intercostal space is a fibrous strait, which marks the entry of a channel between two muscular layers. We describe an aponeurotic channel in which the nerve and vessels run, immediately at the lower border of the cranial rib. The mean total length of intercostal nerve harvested by our technique was 17.86 cm for the ninth intercostal nerve, 16.95 cm for the tenth and 15.75 cm for the eleventh. Bifurcation of the intercostal nerve into a deep branch and the lateral cutaneous branch was found in the majority of the cases, 9.5-21 cm from the emergence of the intercostal nerve in the posterior intercostal space. This anatomical study of the ninth, tenth and eleventh intercostal nerves in the posterior intercostal and lateral intercostal spaces appears to us to allow reliable surgical harvesting.

Effects of surgery on the sensory deficits of syringomyelia and predictors of outcome: a long term prospective study

OBJECTIVE

To quantify the effects of surgery on the thermal deficits of syringomyelia and assess the predictors for such effects.

METHODS

The subjects were 16 consecutive patients (12 men, 4 women; mean (SD) duration of sensory symptoms, 5.1 (4.5) years) presenting with the typical symptoms of syringomyelia related to Chiari I malformation or trauma, and requiring surgical treatment. They were evaluated before surgery, then at six months and two years. Sensory evaluation included determination of the extent of thermal deficits and quantitative assessment of thermal, mechanical, vibration detection, and pain thresholds. Neuropathic pain intensity was evaluated on visual analogue scales. Magnetic resonance imaging was done before and after surgery to measure syrinx dimensions.

RESULTS

The magnitude and extent of thermal deficits improved in a subgroup of patients and this was best predicted by the duration of sensory symptoms: patients operated on less than two years after the onset of their symptoms tended to improve, while those operated on later were stabilised or deteriorated slightly. The effect of surgery on thermal deficits was correlated with the duration of sensory symptoms. Surgery also affected vibration deficits in patients with the Chiari malformation, neuropathic pain on effort, and syrinx dimensions.

CONCLUSIONS

The duration of sensory deficits is the best predictive factor of the efficacy of surgery for the thermal symptoms of syringomyelia. Early surgery is required if these deficits are to be minimised.

Neuroprotective effect of gacyclidine. A multicenter double-blind pilot trial in patients with acute traumatic brain injury

The aim of this study was to assess the safety and efficacy of intravenous (IV) injections of gacyclidine, a novel NMDA receptor antagonist, for neurological and functional recovery following acute traumatic brain injury. This multicenter, prospective, randomized, placebo-controlled, double-blind study compared four parallel groups. Two IV doses were administrated (placebo, 2x0.005mg/kg, 2x0.001mg/kg, 2x0.02mg/kg): the first dose was given within 2 hours following the trauma, and the second dose 4 hours after the first. Fifty-one patients were enrolled and 48 studied between March 1995 and June 1997 in France. Evaluation criteria for safety were physical examination, cardiovascular parameters, blood chemistry, hematology, ECG, and neuropsychological changes monitored after medication. Primary evaluation criteria for efficacy was the Glasgow coma scale complemented by the initial CT-scan and Glasgow outcome scale, motor deficiencies, neuropsychological changes, and functional indenpendence at D90 and D365 or endpoint. Intracranial pressure (ICP) monitoring was not taken into account because all the clinical centers participating in this study did not use this technique in daily practice during the inclusion period. Twelve patients died during the follow-up period, none of these deaths being related to the drug. Serious adverse events (181) were reported by most of the patients with no significant differences between groups. Only 10 of these adverse events were considered to be drug-related. Safety-related laboratory tests did not show any relevant changes. Concerning efficacy, the predefined prognostic factors (initial CT-scan score, initial Glasgow Coma Scale and occurrence of low systolic blood pressure during the first 24 hours) largely determinated the patient's outcome. When the prognostic factors were taken into account together with the dose level in a logistic regression model, gacyclidine showed a beneficial long-term effect and a best dose-result in the 0.04mg/kg treated group. Data obtained in this clinical trial appeared sufficient to warrant a European multicenter study on gacyclidine using the same evaluation criteria and ICP monitoring.

Comparison of dopamine and norepinephrine after traumatic brain injury and hypoxic-hypotensive insult

After severe brain trauma, blood-brain barrier disruption and alteration of cerebral arteriolar vasoreactive properties may modify the cerebral response to catecholamines. Therefore, the goal of the present study was to compare the effects of dopamine and norepinephrine in a model of brain injury that consisted of a weight-drop model of injury complicated by a 15-min hypoxic-hypotensive insult (HH). Sprague-Dawley rats (n = 7 in each group) received, after brain injury, an infusion of either norepinephrine (TNE group) or dopamine (TDA group) in order to increase cerebral perfusion pressure (CPP) above 70 mm Hg. In addition, a control group (C group, no trauma) and a trauma group (T group, brain injury, no catecholamine infusion) were studied. Mean arterial pressure (MAP), intracranial pressure (ICP, intraparenchymal fiberoptic device), and local cerebral blood flow (LCBF, extradural laser-Doppler fiber) were measured throughout the protocol. In T group, brain injury and HH induced a decrease in CPP (by an increase of ICP and a decrease of MAP), and a decrease of LCBF. Both norepinephrine and dopamine failed to increase CPP, and ICP was significantly higher in TNE and TDA groups than in T group. Interestingly, norepinephrine was not able to alleviate the decrease in MAP. Neither norepinephrine or dopamine could induce an increase of MAP. LCBF decreased similarly in T, TNE and TDA groups. In conclusion, norepinephrine and dopamine are not able to restore values of CPP above 70 mm Hg in a model of severe brain trauma. Furthermore, their systemic vasopressor properties are altered.

[Spontaneous regression of paraplegia caused by spontaneous cervico-thoracic epidural hematoma]

Spontaneous spinal epidural hematoma is a rare condition that usually requires surgical treatment in emergency. We report the unusual and well-documented case of a spontaneous spinal epidural hematoma, extending from C6 to T2, occurring in a 56-year old man and causing paraplegia. Without surgery, the paraplegia spontaneously and completely recovered within the first 24 hours. Serial MRI studies demonstrated the remitting course of the spinal epidural hematoma. Emergency surgical evacuation should still be the standard treatment for patients with disabling and/or persistent neurologic deficit. A conservative approach under close neurologic observation may be recommended for patients with no or mild deficits, for patients who show early and continuous clinical improvement within the first 24 hours and for patients with small and/or non-compressive spinal epidural hematoma. Reported cases of spontaneous remission are very rare.

[Imaging of syringomyelia]

This review reports the value of current imaging techniques in the diagnosis of syringomyelia excluding tumoral causes. The value of imaging techniques for evaluation of extension, detection of associated anomalies, and pre- and postoperative evaluation are detailed.

Motoneurons of the adult marmoset can grow axons and reform motor endplates through a peripheral nerve bridge joining the locally injured cervical spinal cord to the denervated biceps brachii muscle

Reconnection of the injured spinal cord (SC) of the marmoset with the denervated biceps brachii muscle (BB) was obtained by using a peripheral nerve (PN) bridge. In 13 adult males, a 45 mm segment of the peroneal nerve was removed: one end was implanted unilaterally into the cervical SC of the same animal (autograft), determining a local injury, although the other end was either directly inserted into the BB (Group A) or, alternatively, sutured to its transected motor nerve, the musculocutaneous nerve (Group B). From 2-4 months post-surgery, eight out of the 10 surviving animals responded by a contraction of the BB to electrical stimulations of the PN bridge. All ten were then processed for a morphological study. As documented by retrograde axonal tracing studies using horse radish peroxidase or Fast Blue (FB), a mean number of 314 (Group A) or 45 (Group B) spinal neurons, mainly located close to the site of injury and grafting, re-expressed a capacity to grow and extend axons into the PN bridge. Most of these regenerated axons were able to grow up to the BB and form or reform functional motor endplates. Many of the spinal neurons that were retrogradely labeled with FB simultaneously displayed immunoreactivity for choline acetyl-transferase and consequently were assumed to be motoneurons. Reinnervation and regeneration of the BB were documented by methods revealing axon terminals, endplates and myofibrillary ATPase activity. Our results indicate that motoneurons of the focally injured SC of a small-sized primate can, following the example of the adult rat, re-establish a lost motor function by extending new axons all the way through a PN bridge connected to a denervated skeletal muscle.

[Horseradish peroxidase retrograde labeling of primary sensory axons in rats: a comparison between three different intraspinal injections methods]

STUDY AIM

In order to improve the results of intraspinal retrograde labeling of post-ganglionic primary sensory axons by horseradish peroxidase (HRP), the authors compared three different intraspinal injection methods of this tracer into the inferior thoracic spinal cord in the rat.

MATERIAL AND METHOD

'Open field' method (group 1, N = 8); stereotactic injection, needle tip diameter = 0.72 mm (group 2, N = 8); stereotactic injection, needle tip diameter = 0.24 mm (group 3, N = 8). Histological features of the spinal injection site showed that tissue damages due to injection was more extensive and deeper than expected. HRP transported in retrograde fashion from injection site to sensory body cells located in dorsal root ganglia (DRG) was revealed by the Mesulam histochemical technique.

RESULTS

The mean number of labeled neurons per DRG was 652 in group 3, 116 in group 2, and 77 in group 1. Differences were statistically significant, especially between groups 1 and 3 (P = 4.10(-16)) and groups 2 and 3 (P = 2.10(-17)).

CONCLUSION

Retrograde labeling of primary sensory axons by HRP (or another axonal tracer) with fine needle stereotactic intraspinal injection may represent an alternative to anterograde labeling. This reliable and reproducible method may be useful in studies dealing with regeneration of post-ganglionic primary sensory axons.

[Treatment of syringomyelia]

Treatment of syringomyelia utilizes two operative approaches: posterior fossa decompression and syrinx shunting (including subarachnoid, pleural and peritoneal shunting). MRI study is nowadays the indispensable tool for the evaluation of patients with syringomyelia and allows to choose the best therapeutic option. Posterior fossa decompression is regarded as the procedure of choice for syringomyelia with Chiari. After intradural exploration, additional steps may be necessary as excision of the cerebellar tonsils. Other therapeutic alternatives are associated with higher complication rates. Patients with persistent focal syrinxes after PFD respond best to syringoperitoneal shunts. For the management of post-traumatic syringomyelia, a large decompressive laminectomy at the fracture site is recommended; the use of a drain does not offer any long-term therapeutic advantage. Syringoperitoneal shunting is the treatment of post-infection syringomyelia but good long-term result is rare in this type of syrinx.

[Syringomyelia and Chiari abnormality in the adult. Analysis of the results of a cooperative series of 285 cases]

This chapter discusses the retrospective data found in 285 patients with syringomyelia associated with Chiari abnormality and collected from 18 neurosurgical departments. A pre and postoperative MRI study and a minimum follow up of at least 2 years were required. A scale of severity was fixed and tested before and after treatment. The size of the cyst, the degree of the foraminal obstruction were analyzed. The mean age at diagnosis was about 39 years and the duration of symptoms about 6.7 years. Sensory disorders were present in 91% of cases, pain in 66% and motor deficit in about 60%. According to our functional classification, the majority of our patients were moderately disabled and only 10.8% showed a severe impotence. Results of the two major surgical procedures, foramen magnum decompression (FMD) (88% of cases) and cyst shunting procedures (SP) (32% of cases) were evaluated with a mean follow-up period of 6.7 years (ranged from 2 to 14 years). Better clinical and morphological results (87% of stabilization or improvement for FMD versus 71% for SP) were obtained by FMD procedure comparing to SP, with the same rate of complications.

[Non-traumatic arachnoiditis and syringomyelia. A series of 32 cases]

We conducted a retrospective study of 32 patients treated for syringomyelia associated with non-traumatic arachnoid scarring. We selected the cases with documented history of arachnoiditis with pre and post-operative clinical evaluation of the neurological status and anatomical study on MRI with a minimal follow-up of one year. Extensive arachnoid scarring (Group I) was noted in 18 cases, after spinal meningitis in 15 cases (tuberculosis in 9 cases, listeria in 3 cases, pyogenic meningitis in 3 cases), subarachnoid hemorrhage in 3 cases. Focal arachnoid scarring (Group II) occurred in 10 cases, related to spinal surgery in 5 cases (meningiomas: 2, neurinomas: 2, thoracic discectomy: 1), to peridural anesthesia in 1 case, thoracic disc herniation in 1 case, Pott's disease in 1 case, no obvious cause in 2 cases. Basal arachnoid scarring without hindbrain herniation (Group III) was associated with birth injuries in 4 cases. Shunting of the syrinx to the subarachnoid or peritoneal cavity was associated with a recurrence rate of 60% whereas microsurgical dissection of the arachnoid scar and decompression of the subarachnoid space with a recurrence rate of 33%, with a mean follow-up period of 28 months. Successful long-term management of the syrinx was associated with basal or focal spinal arachnoid scarring, no history of spinal meningitis, microsurgical dissection of the arachnoid scar and decompression of the subarachnoid space.

[Characterization of sensation disorders and neuropathic pain related to syringomyelia. A prospective study]

The present prospective study aimed to perform quantitative sensory testing (QST) in patients with painful or painless syringomyelia before and after surgical treatment of their syrinx (at 3 and 9 months). Eighteen consecutive patients with cervical or dorso-lumbar syringomyelia completed the study and 9 underwent surgery. Twelve patients had central neuropathic pain (of whom 6 were followed up). Spontaneous pain and brush-evoked allodynia were assessed. Von Frey hairs, vibrameter and a thermotest device were used to determine the mechanical-, vibratory-, thermal-detection thresholds, and the mechanical and thermal pain thresholds. Results showed evidence of deficits in temperature and pain sensibility in 17 cases, often associated with deficits in vibration and touch sensitivity (11 cases). Magnetic resonance scan, including axial images, demonstrated good correlation between paramedian extension of the syrinx and the laterality of thermal deficits. Somatosensory evoked potentials (11 patients) were abnormal in 9 cases at level, and showed good correlation with deficits in vibration. The magnitude of the thermal and tactile deficit was similar between areas of spontaneous pain and adjacent non painful areas. Surgery induced a significant decrease of tactile deficits, and to a lesser extent, of thermal deficits. Effects on neuropathic pain were positive in 3 patients (total disappearance of pain) and negligible or negative in 3 patients, despite collapse of the syrinx (in 2 cases). These results confirm that QST are useful in clinical practice to quantify the clinical results of surgery in patients with syringomyelia, and allow some hypotheses about the mechanisms of neuropathic pain in these patients.

[Imaging of syringomyelia]

MRI is the best imaging method to evaluate syringomyelia. It is important to study from the posterior cranial fossa to the sacro-lumbar region and also the supra-tentorial structures. This complete analysis is essential to classify the syringomyelia and to investigate other associated malformations. Radiographs and CT scan are useful to analyze bone structures. For MRI, the new sequences with phased-array coils are also very important to study the entire spinal cord and the posterior fossa. It is essential to study the spinal cord with sagittal and axial spin echo T1 and fast spin echo T2 weighted images with sometimes coronal view, particularly when the patient presents a scoliosis, to have a correct morphological and functional evaluation. MRI gives an excellent study of the spinal cord with an excellent analysis of a primitive or foraminal syringomyelia, but also traumatic, infectious or post arachnoiditis syringomyelia. Spin echo T1 weighted images with injection of gadolinium can be used if an intra-medullary tumor is suspected. MRI is also useful for the post-operative follow up to evaluate the persistence of the medullary cyst and the enlargement of the foramen magnum.

[Post-traumatic syringomyelia]

Clinical and neuroradiological data were recorded in a series of 73 spinal cord injured patients (33 in Nantes, 40 in Paris-Bicêtre) in whom a post traumatic syringomyelia (PTS) developed. These findings and a review of the literature allow to point out some of the main characteristics in such a pathology. Clinical symptoms are frequent, the commonest of them are pain and sensory loss but any alteration of the neurological status after spinal cord injury has to be considered. Magnetic resonance imaging (MRI), sagittal and axial T1 and T2 weighted images, confirms the diagnosis of syrinx (area with the same signal intensity as CSF extending beyond the site of the initial lesion at least on 2 vertebral segments). MRI allows the diagnosis when it is performed in the follow up of asymptomatic patients. So PTS is not infrequent in spinal cord injured patients, for some of them in the first year after the trauma. The highest incidence is found in patients with complete thoracic lesions. Pathophysiology and surgical management have to take into account post traumatic residual stenosis of the vertebral canal.

Cervical anatomy of phrenic nerve roots in the rabbit. European Group for Research on the Larynx

The cervical anatomy of the different nerve contributions that constitute the phrenic nerve (phrenic nerve roots and accessory phrenic nerve) were studied in rabbits. In 55 dissections, 6 main root arrangement types were observed. The roots that issued from the fourth and fifth cervical nerves (C4 and C5 roots) were constant. The C4 root was either short or long. The C6 root was at times absent, or sometimes double. An accessory phrenic nerve was present in 43% of the right and 28% of the left dissections. The distribution of the phrenic nerve roots often displayed left-right asymmetry. We conclude that a better knowledge of the cervical anatomy of the phrenic nerve is useful both in physiological studies involving diaphragm denervation and in experimental laryngeal reinnervation.

[The place of MRI in the study of cerebrospinal fluid fistulas]

Results of CT and MRI explorations in 8 patients with cerebrospinal fluid (CSF) fistulae are reported and compared with surgical findings in 7. Sensitivity of MRI (CISS and fast T2 spin-echo sequences) was excellent giving perfect correlations with surgical findings in 7/7 cases. CT and MRI were found to provide complementary information suggesting they should be used in combination as first intention explorations of suspected CSF fistulae. Computerized cisternography should be used if MRI is contraindicated or if a clinically and biologically proven CSF fistulae is not visualized by CT or MRI.

[Post-traumatic reconnection of the cervical spinal cord with skeletal striated muscles. Study in adult rats and marmosets]

In an attempt at repairing the injured spinal cord of adult mammals (rat, dog and marmoset) and its damaged muscular connections, we are currently using: 1) peripheral nerve autografts (PNG), containing Schwann cells, to trigger and direct axonal regrowth from host and/or transplanted motoneurons towards denervated muscular targets; 2) foetal spinal cord transplants to replace lost neurons. In adult rats and marmosets, a PNG bridge was used to joint the injured cervical spinal cord to a denervated skeletal muscle (longissimus atlantis [rat] or biceps brachii [rat and marmoset]). The spinal lesion was obtained by the implantation procedure of the PNG. After a post-operative delay ranging from 2 to 22 months, the animals were checked electrophysiologically for functional muscular reconnection and processed for a morphological study including retrograde axonal tracing (HRP, Fast Blue, True Blue), histochemistry (AChE, ATPase), immunocytochemistry (ChAT) and EM. It was thus demonstrated that host motoneurons of the cervical enlargement could extend axons all the way through the PNG bridge as: a) in anaesthetized animals, contraction of the reconnected muscle could be obtained by electrical stimulation of the grafted nerve; b) the retrograde axonal tracing studies indicated that a great number of host cervical neurons extended axons into the PNG bridge up to the muscle; c) many of them were assumed to be motoneurons (double labelling with True Blue and an antibody against ChAT); and even alpha-motoneurons (type C axosomatic synapses in HRP labelled neurons seen in EM in the rat); d) numerous ectopic endplates were seen around the intramuscular tip of the PNG. In larger (cavitation) spinal lesions (rat), foetal motoneurons contained in E14 spinal cord transplants could similarly grow axons through PNG bridges up to the reconnected muscle. Taking all these data into account, it can be concluded that neural transplants are interesting tools for evaluating both the plasticity and the repair capacities of the mammalian spinal cord and of its muscular connections.

[Isolated intramedullary cysticercosis. Case report]

BACKGROUND AND PURPOSE

Cysticercosis is the most common parasitic disease affecting the central nervous system. Although it is still very rare in Europe, the frequency will increase due to the influx of immigrants from the endemic areas and increasing trips in these countries. Spinal intramedullary cysticercosis is an uncommon manifestation of neurocysticercosis.

CLINICAL PRESENTATION

We report a case of pure intramedullary cysticercosis in a young white French girl, presenting as a progressive paraplegia with a cystic lesion in T4 on MRI. The diagnosis was made only after surgery by pathological examination.

CONCLUSIONS

A preoperative diagnosis of spinal intramedullary cysticercosis must be suspected not only in an endemic area in the presence of multiple soft tissue calcifications and segmental lesions revealed by myelography or MRI studies, but also for all cystic lesion of central nervous system even in no endemic area. Surgery is the unique treatment which can be used for spinal intramedullary cysticercosis and with the use of the microsurgical techniques for medullar surgery the outcome is not as dismal as reported earlier.

Axonal regrowth through a collagen guidance channel bridging spinal cord to the avulsed C6 roots: functional recovery in primates with brachial plexus injury

Intraspinal implantation of a collagen guidance channel (CGC) to promote axon regeneration was investigated in marmosets with brachial plexus injury. After avulsion of the right C5, C6 and C7 spinal roots, a CGC containing (group B) or not (group A) a nerve segment, or a nerve graft (group C), was ventro-laterally implanted into the cord to bridge the ventral horn and the avulsed C6 roots. No spinal cord dysfunction was observed following surgery. Two months later, the postoperative flaccid paralysis of the lesioned arm improved. In five months, a normal electromyogram of the affected biceps muscle was recorded in all repaired animals. Motor evoked potentials were obtained with a mean amplitude of 13.37 +/- 13.66 microV in group A, 13.21 +/- 5.16 microV in group B and 37.14 +/- 35.16 microV in group C. The force of biceps muscle contraction was 27.33 +/- 20.03 g (group A), 24.33 +/- 17.03 g (group B) and 37.38 +/- 21.70 g (group C). Retrograde tracing by horseradish peroxidase showed labelled motoneurons ipsilaterally located in the C5 and C6 ventral horn, nearby the implantation site. The mean labelled neurons was 32.33 +/- 21.13, 219.33 +/- 176.29 and 64.33 +/- 23.54 in group A, B and C respectively. Histological analysis presented numerous myelinated and unmyelinated regenerating axons in the implant of these animals. Statistical analysis did not show significant difference among the three repaired groups. Our results indicate that spinal neurons can regenerate through a CGC to avulsed nerve roots and induce motor recovery in primates.

Strong expression of GFAP mRNA in rat hippocampus after a closed-head injury

We investigated the spatiotemporal GFAP mRNA expression over a period of 11 days following brain injury in rats caused by impact acceleration, which is known to produce diffuse axonal injury (DAI). We observed widespread GFAP mRNA expression throughout the brain, which was more rapid and intense in the hippocampus. This expression was obvious in most animals 2 days after injury and appeared maximal at day 6. Although it decreased by day 11, the level of expression remained high compared with control levels. We noted slight differences in time of onset and the magnitude of the response between hippocampus and white matter structures or cortical areas. The different mechanisms able to trigger this response are discussed in regard to histopathological changes observed in DAI models.

Selective resection of the phrenic nerve roots in rabbits. Part II: Respiratory effects

This study evaluates the delayed respiratory consequences of selective resection of one or several roots of the right phrenic nerve in rabbits. A total of 50 animals were operated on according to five modalities of root resection. A total of 11 animals served as control. The breathing pattern was analysed 8 weeks after surgery. Transdiaphragmatic pressure was measured during transjugular supramaximal stimulation of the phrenic nerve, unilaterally or bilaterally and during prolonged tracheal occlusion (PImax). No difference was observed between the esophageal pressure observed during bilateral phrenic nerve stimulation (BilPeso) in control animals when compared to animals with resection of the highest root of the right phrenic nerve (16.2 +/- 1.0 versus 14.5 +/- 1.0 cmH2O (mean +/- SE). Resection of the two highest or of the two lowest roots of the right phrenic nerve resulted in a similar BilPeso (11.3 +/- 0.8 versus 11.1 +/- 1.2 cmH2O). Preservation of only the accessory phrenic nerve (PN) resulted in a low value of BilPeso (9.8 +/- 1.0 cmH2O) similar to that obtained with complete denervation of the right hemidiaphragm. Ventilation and PImax were not different between the denervated or intact rabbits during quiet breathing. We conclude that in rabbits: (1) Diaphragmatic function is preserved after resection of the highest root of the phrenic nerve. (2) Diaphragmatic function is altered if only the APN is preserved.

[A study of the influence of sutures and tension on skin cicatrization in loss of substance in 18 minipigs]

This study concerned the evaluation of wound healing after extensive skin resections in 18 minipigs, sutured with: continuous intradermal Polyglactin 910 suture or Polyamide, an interrupted intradermal sutures using the same resorbable suture material. Three equivalent groups were studied: 0, 3 and 6 cm skin resections were studied after using a dynamometer to record the tension necessary to join the wound margins. Results were evaluated 1 month later by light and electron microscopy, and were statistically correlated by Pearson's test. The wound tension was correlated with skin resection (r = 0.97, p < 10-4). The scar width was exponentially correlated with tension (r = 0.70, p < 10-3); the fibrous and cellular appearances increased with the skin resection. The absence of any significant statistical results prevents any conclusion concerning the superiority of one suture material or suture technique, but the group with no resection led to homogenous results, regardless of the suture technique, or suture material used. 3 and 6 cm resection the groups led to unpredictable and various results. Granulous reactions were observed in 7 out of 12 cases with resorbable suture, and only 1 of the 8 cases with non resorbable suture, but these results are not significant.

[Multicenter coordination and future strategy in spinal cord injuries]

Recovery of neurologic function after traumatic injury to the spinal cord can be significantly improved provided prompt medico-surgical decision is being taken, aiming at limiting post traumatic tissue damages extension. In an effort to optimize the triage of these patients, we set a multicentric emergency network program, involving cooperating staff from first care, surgical and rehabilitation departments. This program has allowed us to reduce substantially the time between trauma and medico-surgical treatment. Our first objective was to obtain spinal cord decompression and spinal stabilization as quickly as possible, the set-time limit being 8 hours at most after trauma. This emergency network being operational, we started a multicentric study to test whether the neurologic recovery following a spinal cord injury could be further improved by adding.