Computed tomography in syringomyelia and the associated Arnold-Chiari type I malformation

Spontaneous regression of syringomyelia in a young patient with Chiari type I malformation

Syringomyelia is a disorder in which a cyst or cavity forms within the spinal cord. This cyst, called syrinx, can expand and elongate over time, destroying the spinal cord. We describe the case of a young patient with partial spontaneous regression of syringomyelia in Chiari I malformation, confirmed by magnetic resonance imaging three years after the diagnosis. During this period the patient did not experience any clinical symptoms. Although described in literature, spontaneous regression is an unusual event and very few cases have been reported. This case report supports the belief that conservative management together with both clinical and imaging periodic controls should be preferred in stable mild-symptomatic patients.

Pathogenesis of syringomyelia associated with Chiari type 1 malformation: review of evidences and proposal of a new hypothesis

The exact pathogenesis of syringomyelia associated with Chiari type 1 malformation is unknown, although a number of authors have reported their theories of syrinx formation. The purpose of this review is to understand evidences based on the known theories and to create a new hypothesis of the pathogenesis. We critically review the literatures on clinicopathological, radiological, and clinical features of this disorder. The previously proposed theories mainly focused on the driven mechanisms of the cerebrospinal fluid (CSF) into the spinal cord. They did not fully explain radiological features or effects of surgical treatment such as shunting procedures. Common findings of the syrinx in clinicopathological studies were the communication with the central canal and extracanalicular extension to the posterior gray matter. Most of the magnetic resonance imaging studies demonstrated blockade and alternated CSF dynamics at the foramen magnum, but failed to show direct communication of the syrinx with the CSF spaces. Pressure studies revealed almost identical intrasyrinx pressure to the subarachnoid space and decreased compliance of the spinal CSF space. Recent imaging studies suggest that the extracellular fluid accumulation may play an important role. The review of evidences promotes a new hypothesis of syrinx formation. Decreased absorption mechanisms of the extracellular fluid may underlie the pathogenesis of syringomyelia. Reduced compliance of the posterior spinal veins associated with the decreased compliance of the spinal subarachnoid space will result in disturbed absorption of the extracellular fluid through the intramedullary venous channels and formation of syringomyelia.

Definition of the adult Chiari malformation: a brief historical overview

With the widespread use of newer neuroimaging techniques and modalities, significant tonsillar herniation is being diagnosed in more than 0.5% of patients, some of whom are asymptomatic. This puts the definition of the adult Chiari malformation to the test. The author provides a historical review of the evolution of the definition of the adult Chiari malformation in the neurosurgery, radiology, and pathology literature.

Syringohydromyelia following meningomyelocele surgery--role of metrizamide myelography and computed tomography

Five children developed symptoms attributable to syringohydromyelia several years following neonatal surgery for lumbosacral meningomyelocele. Metrizamide injection followed by computed tomography (CT) was performed in all five patients. In two patients, there was direct opacification of both the subarachnoid space and the syringohydromyelia. In a further two patients, delayed CT demonstrated late opacification of the central cavity from contrast introduced into the subarachnoid space. In the fifth patient via a suboccipital puncture, there was fortuitous filling of a caudally displaced fourth ventricle communicating with a central cavity within the cord, but there was no visualization of the subarachnoid space. Surgery with decompression and plugging of the obex halted the progression of the disease in all the patients.

Chiari malformation type I: a new MRI classification

Thirty patients with Chiari I malformation were examined by MRI over 2-year period. All patients underwent MRI scan before and after surgical decompression of the posterior fossa. Images of the craniocervical junction confirmed tonsillar herniation in all cases and allowed the definition of two anatomically distinct types of Chiari malformation. Twenty-one of the 30 patients (70%) had concomitant syringomyelia and were classified as type A, while the remaining 9 patients (30%) had evidence of frank herniation of the cerebellar tonsils below the foramen magnum without evidence of syringomyelia and were labeled type B. Type A patients had a predominant central cord symptomatology; type B patients exhibited signs and symptoms of brain stem or cerebellar compression. The concomitant cord cavitary lesions (syringomyelia) were noncommunicating (isolated syrinxes), which were separated from the fourth ventricle by a syrinx-free segment of normal spinal cord. Holocord hydromyelic cavities were seen in 8 out of 21 patients with syringomyelia, isolated cervical cavities were seen in 4 patients, while combined cervical and thoracic cavities were seen in 9 patients. Kinking of the medullocervical junction and brain stem was seen in 20 out of 30 patients (67%). MRI has proved to be an excellent, noninvasive means of studying of the craniocervical anatomy; it has allowed a classification of Chiari malformation based on objective anatomic criteria with prognostic and clinical relevance.

Cerebrospinal fluid flow dynamics study in Chiari I malformation: implications for syrinx formation

Cerebrospinal fluid (CSF) flow abnormalities are known to be present in Chiari I malformation and to underlie the origin and progression of associated syringomyelia. The incidence of syrinx formation, however, is variable for unknown reasons. The aim of this study was to investigate whether differences in CSF flow dynamics in patients with Chiari I malformation may account for the different clinical and radiological presentation.

Presurgical and postsurgical phase-contrast magnetic resonance imaging investigations were prospectively conducted in 47 adult patients with symptomatic Chiari I malformation. Patients were divided into two groups according to the presence (32 cases) or absence (15 cases) of syrinx. Cerebrospinal fluid flow patterns were evaluated at four regions of interest: prebulbar cistern, foramen magnum, and the ventral and dorsal spinal subarachnoid spaces at the C-5 level. A temporal analysis of CSF flow waveforms was performed with measurement of cranial- and caudal-directed flow durations. All patients underwent a craniocervical decompressive procedure. Preoperatively, a prolonged caudal-directed (systolic) flow pattern was observed in patients with syringomyelia, as compared with normal control values obtained in 15 healthy volunteers. Conversely, a decreased systolic duration was observed in Chiari I patients who had malformation without syrinx. These trends were not statistically significant because of the considerable degree of overlap with the control values recorded in both groups. Additional comparison of the observed preoperative values obtained in patients with and those without syringomyelia indicated that the difference in systolic flow duration was significant at the ventral spinal subarachnoid space level (p = 0.003) and remarkable at the other levels, although not reaching statistical significance. Cerebrospinal fluid flow was minimal or absent at the foramen magnum (dorsal aspect) due to tonsillar herniation, precluding reliable quantitative measurement at this level. There was no evidence of communication between the fourth ventricle and syrinx in any case. Postoperatively, unobstructed CSF flow was recorded across the enlarged foramen magnum and into the artificial cisterna magna in all patients. A gradual restoration of near-normal flow patterns was observed in both groups. Inside the syrinx, fluid motion gradually tapered, no longer being detectable in 12 patients (37.5%) 1 year postsurgery.

In patients with Chiari I malformation and associated syringomyelia different CSF flow patterns were demonstrated as compared with patients in whom syrinx was absent. Analysis of this study's findings supports the hypothesis that in Chiari I malformation an elongated systolic flow may prolong the condition of increased spinal subarachnoid pressure caused by the junctional obstruction, thus favoring CSF penetration into the spinal cord. It may be also proposed that a shortened systolic flow may be insufficient to maintain a hypertensive condition for enough time to induce syrinx formation.

Acquired Chiari I malformation and syringomyelia associated with bilateral chronic subdural hematoma. Case report

The authors report a case of bilateral chronic subdural hematoma in a 25-year-old woman who had occipital and neck pain. Magnetic resonance imaging revealed progressive caudal descent of the cerebellar tonsils (acquired Chiari I malformation) and a large eccentric syrinx in the spinal cord from the C3-T7 levels. Spontaneous disappearance of the chronic subdural hematomas resulted in radiographic resolution of both lesions, as well as clinical improvement. Theories of syringomyelia formation, the relationship to acquired Chiari I malformation, and the implications of this case are discussed.

"Acquired" Chiari I malformation. Case report

Tonsillar descent of the cerebellum in Chiari I malformations is often considered a congenital defect. A patient is presented in whom magnetic resonance (MR) imaging revealed normally positioned cerebellar tonsils; however, 1 year later MR imaging was repeated for evaluation of gait abnormalities and showed descent of the cerebellar tonsils. This case illustrates worsening symptoms with progressive descent of the cerebellar tonsils and suggests that Chiari I malformations can evolve postnatally.

Syringomyelia in children: six case reports and review of the literature

We present six cases of syringomyelia in children below the age of 16 years seen during the last 8 years at the neurosurgical departments in the west of Yorkshire. The clinical presentation of syringomyelia in children is different from that in adults and magnetic resonance imaging is the investigation of choice. Because of the natural history of syringomyelia, the long-term results of surgical treatment are very difficult to evaluate accurately. Although our series is small, it does highlight the presentations and the methods of investigation. The diversity of pathology is noted; in particular any associated hydrocephalus or intramedullary tumour.

Hydromyelic hydrocephalus. Correlation of hydromyelia with various stages of hydrocephalus in postshunt isolated compartments

The clinical features and pathophysiology of specific forms of hydromyelia are analyzed in this report together with the chronological changes of associated hydrocephalus. Nine patients were studied; all had hydromyelia with varying degrees of associated hydrocephalus. Clinically applicable classification systems were used to evaluate the progression of hydrocephalus (Stages I to IV) and to define the compartment isolated after shunting in the previously communicating cerebral ventricles (Types I to IV). Four patients had Stage IV disease (holoneural canal dilatation); one had Stage II and four had Stage I disease (both Stages I and II with supratentorial hydrocephalus). All patients were initially treated by ventriculoperitoneal shunting at an average age of 9.9 years. Five patients had progressive spinal symptoms before or after treatment of their hydrocephalus. Two patients had Type III isolation (an isolated rhombencephalic ventricle) with a functioning ventricular shunt; ventriculography confirmed a communication between the fourth ventricle and the hydromyelia, and both patients improved after placement of a shunt in the fourth ventricle. The remaining patients had Type IV isolation (isolated central canal dilatation) with a functioning ventricular shunt. This study indicates that in some cases the pathophysiology of hydromyelia is closely related to associated hydrocephalus. A new concept of the development of an isolated compartment after shunting is proposed to explain the progression of hydromyelia in these cases.

Basichondrocranium anomalies in adult Chiari type I malformation: a morphometric study

The purpose of this study was to determine the frequency of anomalies of the basichondrocranium in a series of 42 patients with Chiari type I malformation compared with a control group of 46 subjects. Sixteen patients also had syringomyelia. Linear, angular and posterior fossa surface area measurements were taken on conventional lateral skull x-rays. Posterior fossa volume was estimated by CT scanning. In patients there was shortening of clivus length, Twining-opisthion distance and Chamberlain's line. Basal and Boogard angles were enlarged. The size of the posterior fossa was smaller in patients than in controls. Only 10 (23.8%) patients had no evidence of occipital dysplasia. When discriminant analysis was applied to the data, the most discriminative variables were posterior fossa area and clivus length which allowed accurate identification of 76% of patients as belonging to the patient group and 79% of controls as belonging to the control group. These findings prove that under-development of the basichondrocranium with a small size of the posterior fossa is an outstanding feature in adult Chiari type I malformation, and support the hypothesis that tonsillar ectopia is secondary to the disproportion between the posterior fossa and the cerebellum, which is forced to grow into the cervical spinal canal.

Hydromyelia: a critical review

The author reviews current concepts involving the etiology, pathogenesis, and treatment of hydromyelia. A critical evaluation of current surgical approaches in relation to the type of hydromyelia present is discussed.

Chiari I malformation with quadriplegia and respiratory disturbance in an infant

Chiari I malformation consists of variable downward displacement of the cerebellar tonsils. Quadriplegia, respiratory disturbance and pain are common in Chiari I malformation in adults. However, there are no reports of this syndrome in early childhood. We report the case of a 9-month-old girl with Chiari I malformation who had quadriplegia with muscle weakness and who developed respiratory disturbance as an early symptom. The causes of the symptoms of Chiari I malformation are discussed. The use of MRI is proposed as a more useful diagnostic technique than myelography for these patients since MRI is less likely to aggravate the respiratory disturbance.

The incidence of craniocervical bony anomalies in the adult Chiari malformation

Detailed linear, angular and surface area measurements were undertaken on the lateral skull radiographs of 32 patients with proven idiopathic adult Chiari type 1 malformation. Basal angles were larger, the clivus was shorter and Klaus' index was reduced in patients compared to normal controls. The size of the posterior fossa was smaller in patients than in controls. By discriminant analysis of the skull X-ray data it was possible to identify correctly two thirds of patients as belonging to the patient group. The findings indicate that craniocervical bony anomalies in the adult Chiari malformation are commoner than was previously realised, and they support the view that tonsillar herniation in these patients results from bony occipital dysplasia.

Acute paraparesis secondary to Arnold-Chiari type I malformation and neck hyperflexion

A 2-year-old child experienced clinical manifestations of Arnold-Chiari Type I malformation, rare in early childhood, after a mild hyperflexion injury of the neck that resulted in acute paraparesis. Recovery occurred after decompressive laminectomy.

Chiari malformation in adults: a review of 40 cases

Forty adult patients (average age 40 years), with the clinical and radiological features of the Chiari malformations, were seen at the Toronto Western Hospital between 1967 and 1984. Surgical confirmation of the diagnosis was obtained in 32 cases; of these, 23 were classified as Chiari I malformation while 9 fulfilled the anatomic criteria of Chiari II. The patient population consisted of 22 males and 18 females. Common presenting symptoms included head and neck pain (60%), sensory complaints (60%), upper extremity weakness (42%), and gait disturbance (40%). Neurological findings included signs of central cord dysfunction (73%), long-tract motor and/or sensory findings (58%), brainstem signs (38%), cerebellar dysfunction (18%), and increased intracranial pressure (15%). The majority of patients underwent myelography with or without computed tomography of the cervical-medullary junction. Two recent patients had 0.15T MRI scans which helped demonstrate an intramedullary syrinx. Thirty-three patients underwent 47 operative procedures (discounting spinal fusion and CSF shunt revisions). Open surgical management was performed in 32 patients, with CSF shunting along in one patient. Five patients (15%) incurred surgical complications within a six week postoperative period. Follow-up to date, ranges from one month to 11 years. In the 33 surgically treated patients, 18 are improved (55%), 10 are neurologically stable (30%), and five have worsened clinically (15%), including one death. Based on this study it appears that the Chiari II malformation may be more common in adults than previously recognized. Surgical intervention has a favourable outcome in the majority of patients but a significant proportion continue to deteriorate.

Use of the syringoperitoneal shunt in the treatment of syringomyelia

A syringoperitoneal shunt is a one-way drain that empties cerebrospinal fluid from the pathological syringomyelic cavity into the abdomen. This treatment technique is based on the principle that the signs and symptoms of syringomyelia are caused by insidious interference with the condition of nerve signals in the spinal cord tracts due to either tearing or compression of the tracts by the distended cavity. A series of eight patients suffering from this disorder were operated upon using a syringoperitoneal shunt. The initial results seem to indicate that this technique is especially useful when pain, atrophy, or both dominate the clinical picture. Clinical signs, diagnostic studies, and surgical considerations are discussed.

Computed tomographic myelography (CTM) in atlanto-axial rheumatoid arthritis

Thirty-two patients with severe cervical rheumatoid arthritis were investigated preoperatively with cervical myelography (CeM) and computed tomographic myelography (CTM). The severity of their clinical symptoms correlated excellently with a combination of the deformation of the spinal cord at the atlanto-axial level, the lateral dislocation of the cord at the same level, and the deformation of the cord at some lower cervical level. Obstructing soft-tissue excrescences seemed to have little significance. No correlation was found in this study between the deformation of the cord and the main findings of the plain films: the atlanto-axial subluxation (AAS), the vertical subluxation (VS), or their combination.

Is there an increased risk of early side effects of metrizamide in post-myelogram computed tomography?

The safety of post-myelogram computed tomography (PMCT) as an additional diagnostic procedure to metrizamide myelography was evaluated. One hundred and four consecutive patients with suspected cervical cord lesions were studied prospectively; 50 had both myelography and PMCT, and the 54 acting as controls had only myelography. PMCT did not increase the incidence, severity or duration of common side effects and the majority of patients accepted this additional procedure. It is concluded that as long as care is taken to avoid the occurrence of excessive contrast in the intracranial subarachnoid space, PMCT is a safe procedure.

Occipital dysplasia and Chiari type I deformity in a family. Clinical and radiological study of three generations

Three generations of a family affected by a craniocervical malformation (CCM) were subjected to clinical and radiological studies. Occipital dysplasia (OD) and Chiari type I deformity (CD.I) were the main features, inheritance being autosomal-dominant. The malformation was variably expressed; it ranged from OD with basilar impression (BI) to OD without BI and from CD.I with OD to CD.I without obvious osseous malformation. Its pathogenesis, and that of other related familial disorders (Klippel-Feil syndrome and syringomyelia), is discussed, the conclusion being drawn that all were elements of one genetic disorder which finds expression in a very variable sequence. The value of high-resolution CT in the detection of asymptomatic carriers is emphasized.

Computer-tomographic investigations in malformations of the occipito-cervical junction

The diagnosis of occipito-cervical dysplasias has been improved markedly by computer-tomography. Two millimetre transverse cuts with sagittal and coronal reconstructions are necessary. Based on nine cases with nearly all types of malformations it is shown that even complex osseous (mesodermal) malformations and dysplasias as well as isolated or combined neuroectodermal dysplasic or secondary compressive lesions of the medulla oblongata and cord can be detected. Transverse and AP diameters of the foramen magnum and spinal canal and the classical lines and angles can be measured. This time-consuming procedure will give more information than the classical radiological methods and avoid myelographic and cisternal examinations. Its disadvantages are the impossibility of dynamic functional studies and the length of the procedure.

Computed tomography in the diagnosis of syringomyelia

We describe the usefulness of computed tomography (CT) in the diagnosis of syringomyelia in 12 patients for whom the diagnosis had remained unconfirmed with other diagnostic methods. In 7 of these patients, CT myelography revealed an intramedullary cavitation filled with contrast medium. In 3 patients, the cavitation was not filled, and positive contrast medium was not used in another 2. In these 5 cases, however, CT visualized low-density areas within the cord. CT would seem to be the most preferable method for confirming the clinical diagnosis of syringomyelia and is particularly useful in atypical cases.

Arnold-Chiari malformation. Review of 71 cases

The natural history of symptomatic adult Type I Arnold-Chiari malformation (ACM) is variable, and the value of surgery in the management of this disease is difficult to assess. A series of 71 patients in whom a diagnosis of Type I ACM was confirmed at operation is presented, and the progress of the patients following posterior fossa decompression is analyzed. The length of history varied greatly. Pain was the commonest symptom (69% of patients); other symptoms included weakness (56%), numbness (52%), and unsteadiness (40%). The presenting physical signs consisted of a foramen magnum compression syndrome (22%), central cord syndrome (65%), or a cerebellar syndrome (11%). Myelography was performed in 69 patients, and was the most useful investigation. Only 23% of plain radiographs were abnormal. In addition to tonsillar descent, the operative findings included arachnoid adhesions (41%) and syringomyelia (32%). All patients underwent suboccipital craniectomy and C1-3 laminectomy. Respiratory depression was the most frequent postoperative complication (14%), and one patient died from sleep apnea. Early postoperative improvement of both symptoms (82%) and signs (70%) was followed by later relapse in 21% of patients, showing an initial benefit following surgery. None of the patients with a cerebellar syndrome deteriorated, whereas 56% of patients with evidence of foramen magnum compression and 66% of those with a central cord syndrome maintained their initial improvement. The authors conclude that posterior fossa decompression appears to benefit some patients, although a significant proportion might be expected to relapse within 2 to 3 years after operation, depending upon the presenting syndrome.

Use of invasive neuroradiological investigations in patients with normal computerised tomography

A review of the results of neuroradiological investigation of patients in whom computed tomography had shown no intracranial abnormality showed that the use of invasive studies, particularly pneumoencephalography, has declined since installation of a computed tomography scanner, and indications for such studies have become firmer. Diagnostic yield from invasive procedures in patients presenting with epilepsy, dementia, headache (including facial pain), or loss of consciousness is negligible.

Considerations in the diagnosis and treatment of syringomyelia and the Chiari malformation

A series of patients with abnormalities of the craniocervical junction with and without syringomyelia is reviewed. The impact of computerized tomography scanning on current radiological evaluation is discussed. Air myelography may no longer be necessary for accurate diagnosis. While the results of surgery for the Chiari malformation were good, at least one-half of the patients with syringomyelia showed continued progression of symptoms after posterior fossa surgery. More effective surgical therapy requires a better understanding of the pathogenesis of the syrinx.

Computed tomography of "cystic" intramedullary lesions

Using an EMI 5005 scanner with high resolution option, 75% of syrinxes were shown as low density cavities. Most spinal cord tumours caused isodense swellings, but 41% contained low density zones and cystic elements were demonstrated in 76% of these at surgery or by puncture of the spinal cord; a few (11%) of the isodense tumours were cystic. The differential diagnosis of low density intramedullary lesions is discussed.

Arnold-Chiari malformation detected by unenhanced multiplanar CT scan

Multiplanar computed tomographic (CT) scanning done without injection of contrast agent detected the nervous tissue abnormalities in 4 patients with Arnold-Chiari Malformation. Comparisons were made between traditional radiological studies and CT scanning. Three cases were confirmed surgically; the fourth case was diagnosed purely by CT scanning. This preliminary study suggests that this new technique should be sufficient to make a positive diagnosis in most cases of Arnold-Chiari malformation.

Computed tomography of the spine and spinal cord; limitations and applications

The author presents a comprehensive review of the literature on spinal computerized tomography in the evaluation of spinal fractures and fracture-dislocations, degenerative processes with bony encroachment into the spinal canal, disc protrusion, cystic degeneration of the cord, communicating hydro-syringomyelia, intra- and extramedullary neoplasms and congenital malformations. Critical analysis of all published data and additional personal experience gained over the past three years make it possible to better define the clinical applications and practical limitations of spinal CT scans.

Clinical relevance of radiological abnormalities of the craniovertebral junction

Clinical review of a large series of lesions of the craniovertebral angle revealed that no abnormality could be shown by radiological means in 30-50% of cases. Conversely, 30-50% of radiologically demonstrable skeletal disorders at the craniovertebral angle were asymptomatic.

Radiographic studies of the ventricles in syringomyelia

Radiographic investigations of 171 patients with "communicating' syringomyelia have been reviewed. Hydrocephalus was found in one-third of the cases and has occasionally progressed after operation on the posterior fossa, sometimes with accompanying clinical deterioration. The outlets of the fourth ventricle were usually abnormal; tonsillar descent, arachnoiditis and both together were seen. Arachnoiditis correlated strongly with a history of difficult birth. The foramen of Magendie was sometimes patent and sometimes blocked. There was no consistent level of occlusion corresponding to a persistent roof of the fourth ventricle. The cisterna magna was usually small or obliterated but some examples of large cisterns or subarachnoid pouches were found. Radiological demonstration of a communication from the fourth ventricle to the syrinx occurred in only seven patients by positive contrast material and not by air. It is suggested that a sizable communication is rare at the time when patients seek treatment.

Morphology of the cervical spinal cord on computed myelography

To ensure adequate use of the technique of computed myelography (CM) it is necessary to have an exact picture of the morphology of the normal spinal cord as demonstrated by this technique. This has been obtained by studying the morphology and measuring the frontal and sagittal diameter of the cervical cord in 20 patients. The normal values are presented. The changes of this morphology in one patient with a tumour, one patient with atrophy of the spinal cord and in some patients with congenital malformations are also reported.