Pathological basis of spinal cord cavitation in syringomyelia: analysis of 105 autopsy cases

This report summarizes neuropathological, clinical, and general autopsy findings in 105 individuals with nonneoplastic syringomyelia. On the basis of detailed histological findings, three types of cavities were distinguished: 1) dilations of the central canal that communicated directly with the fourth ventricle (47 cases); 2) noncommunicating (isolated) dilations of the central canal that arose below a syrinx-free segment of spinal cord (23 cases); and 3) extracanalicular syrinxes that originated in the spinal cord parenchyma and did not communicate with the central canal (35 cases). The incidence of communicating syrinxes in this study reflects an autopsy bias of morbid conditions such as severe birth defects. Communicating central canal syrinxes were found in association with hydrocephalus. The cavities were lined wholly or partially by ependyma and their overall length was influenced by age-related stenosis of the central canal. Non-communicating central canal syrinxes arose at a variable distance below the fourth ventricle and were associated with disorders that presumably affect cerebrospinal fluid dynamics in the spinal subarachnoid space, such as the Chiari I malformation, basilar impression, and arachnoiditis. These cavities were usually defined rostrally and caudally by stenosis of the central canal and were much more likely than communicating syrinxes to dissect paracentrally into the parenchymal tissues. The paracentral dissections of the central canal syrinxes occurred preferentially into the posterolateral quadrant of the spinal cord. Extracanalicular (parenchymal) syrinxes were found typically in the watershed area of the spinal cord and were associated with conditions that injure spinal cord tissue (for example, trauma, infarction, and hemorrhage). A distinguishing feature of this type of cavitation was its frequent association with myelomalacia. Extracanalicular syrinxes and the paracentral dissections of central canal syrinxes were lined by glial or fibroglial tissue, ruptured frequently into the spinal subarachnoid space, and were characterized by the presence of central chromatolysis, neuronophagia, and Wallerian degeneration. Some lesions extended rostrally into the medulla or pons (syringobulbia). Although clinical information was incomplete, simple dilations of the central canal tended to produce nonspecific neurological findings such as spastic paraparesis, whereas deficits associated with extracanalicular syrinxes and the paracentral dissections of central canal syrinxes included segmental signs that were referable to affected nuclei and tracts. It is concluded that syringomyelia has several distinct cavitary patterns with different mechanisms of pathogenesis that probably determine the clinical features of the condition.

Posterior fossa volume and response to suboccipital decompression in patients with Chiari I malformation

Smaller posterior fossa (PF) volume has been suggested to be one of the mechanisms responsible for tonsillar herniation through the foramen magnum in patients with Chiari I malformation (CM I). Although previous radiological analyses of the cranial anatomy have suggested a smaller PF volume in patients with CM I, the relationship of the PF volume to decompressive surgery has not been reported. We have measured the ratio of PF volume to supratentorial volume (PF ratio [PFR]) in 20 patients with CM I and 20 control patients by retrospectively studying their magnetic resonance images with a computerized image analyzer. The mean PFR in patients with CM I (with or without syringomyelia) was significantly smaller than for those in the control group (15.6 +/- 1.9 versus 17.5 +/- 1.2, P = 0.0008). Although PFR did not correlate with the extent of tonsillar herniation in patients with CM I, it did directly correlate with their age, i.e., younger patients with CM I (but not control patients) had smaller PFRs. All but three patients responded both clinically and radiographically to decompressive surgery. Those patients who did not benefit from surgical intervention had normal PFRs. We conclude that: 1) PFRs are smaller in most patients with CM I; 2) a smaller PF may be a primary cause of tonsillar herniation; 3) patients with CM I who have smaller PFRs tend to develop symptoms earlier than those with normal values; 4) patients with smaller PFRs tend to respond better to suboccipital decompression.

Chiari malformation presenting in adults: a surgical experience in 127 cases

We reviewed 127 patients who were operated upon for adult presentation Chiari malformation and made six conclusions: (a) The clinical examination remains crucial in the diagnosis. (b) The surgical anatomy is highly varied. (c) Syrinxes can be missed on preoperative contrast studies. (d) By a conservative grading system, we determined that 46% of the patients improved during long term follow-up. One-quarter deteriorated over the long run in spite of any treatment. (e) The overall results did not differ whether the treatment was plugging of the central canal plus decompression or decompression alone. (f) In patients with progression, plugging of the central canal obtained superior results. A review of the literature shows that the natural history of this complex disease process has not been established. This history is needed to identify the course of what may be several important factors that lead to the pathological condition in this disease.

On the Pathogenesis of Syringomyelia: A Review

Discussion of the pathogenesis of syringomyelia involves considering the origin of the fluid and also the forces which cause that fluid to break down the structure of the cord. When cerebrospinal fluid (CSF) appears to be the destructive element, it commonly enters through a patent central canal running from the fourth ventricle to the inside of the syrinx. In both clinical and experimental situations pressure differences may be measured which suck on the hindbrain, particularly the cerebellar tonsils, producing deformities. These pressure differences may also suck fluid into the syrinx. In other cases, even when a communication does not appear to be patent, the hindbrain abnormalities are usually present and suck effect may usually be demonstrated and its correction be accompanied by clinical improvement. Other sources of fluid within a syrinx include liquefaction of haematomata after traumatic paraplegia and transudation of fluid from intrinsic spinal tumours. Once fluid is present within a cord cavity it may pulsate upwards and downwards in response to fluid movements in the subarachnoid space, the most energetic of which result from venous influences. Such movement, ‘slosh’, may cause the cavities to extend at either end giving rise to upward and downward extension from a post-traumatic cord cyst and sometimes to syringobulbia. Cord ischaemia, venous congestion and transport of fluid along perivascular spaces may all play a part in the maintainance of cord cavities or the progression of the clinical disabilities.

Surgical management of spinal cord hemangioblastomas in patients with von Hippel-Lindau disease

OBJECT

Von Hippel-Lindau (VHL) disease is an autosomal-dominant disorder frequently associated with hemangioblastomas of the spinal cord. Because of the slow progression, protean nature, and high frequency of multiple spinal hemangioblastomas associated with VHL disease, the surgical management of these lesions is complex. Because prior reports have not identified the factors that predict which patients with spinal cord hemangioblastomas need surgery or what outcomes of this procedure should be expected, the authors have reviewed a series of patients with VHL disease who underwent resection of spinal hemangioblastomas at a single institution to identify features that might guide surgical management of these patients.

METHODS

Forty-four consecutive patients with VHL disease (26 men and 18 women) who underwent 55 operations with resection of 86 spinal cord hemangioblastomas (mean age at surgery 34 years; range 20-58 years) at the National Institutes of Health were included in this study (mean clinical follow up 44 months). Patient examination, review of hospital charts, operative findings, and magnetic resonance imaging studies were used to analyze surgical management and its outcome. To evaluate the clinical course, clinical grades were assigned to patients before and after surgery. Preoperative neurological status, tumor size, and tumor location were predictive of postoperative outcome. Patients with no or minimal preoperative neurological dysfunction, with lesions smaller than 500 mm3, and with dorsal lesions were more likely to have no or minimal neurological impairment. Syrinx resolution was the result of tumor removal and was not influenced by whether the syrinx cavity was entered.

CONCLUSIONS

Spinal cord hemangioblastomas can be safely removed in the majority of patients with VHL disease. Generally in these patients, hemangioblastomas of the spinal cord should be removed when they produce symptoms or signs.

The pathogenesis of syringomyelia associated with lesions at the foramen magnum: a critical review of existing theories and proposal of a new hypothesis

Syringomyelia is frequently accompanied by an extramedullary lesion at the foramen magnum, particularly a Chiari I malformation. Although syringomyelia associated with foramen magnum obstruction has characteristic clinical, radiological, and neuropathological features, its pathogenesis remains unclear. Currently prevalent hydrodynamical theories assert that obstruction of the subarachnoid space at the foramen magnum interferes with flow of cerebrospinal fluid (CSF) between the spinal and the intracranial subarachnoid compartments. As a result, spinal CSF is driven into the spinal cord through the perivascular spaces to form a syrinx. These theories are implausible biophysically because none postulates a pump adequate to drive fluid through these spaces. None of the theories can explain why syrinx pressure is higher than CSF pressure; why extensive gliosis, edema, and vascular wall thickening regularly occur; and why the composition of syrinx fluid is not identical with that of CSF. A new theory of pathogenesis is proposed to address these difficulties. In the presence of subarachnoid obstruction at the foramen magnum, a variety of activities, such as assuming the erect posture, coughing or straining, and pulsatile fluctuations of CSF pressure during the cardiac cycle, produce transiently higher CSF pressure above the block than below it. There are corresponding changes in transmural venous and capillary pressure favoring dilation of vessels below the block and collapse of vessels above the block. The spatially uneven change of vessel caliber produces mechanical stress on the spinal cord, particularly caudal to the block. The mechanical stress, coupled with venous and capillary dilation, partially disrupt the blood-spinal cord barrier, allowing ultrafiltration of crystalloids and accumulation of a protein-poor fluid. The proposed theory is consistent with the neuropathological findings in syringomyelia and with the pressure and composition of syrinx fluid. It also accounts for the prolonged course of syringomyelia and its aggravation by cough, strain, and assumption of an erect posture. It contributes to understanding the low incidence and the morphology of syringobulbia. It explains the poorly understood presentation of foramen magnum meningiomas with symptoms of a mid- to low-cervical myelopathy. The theory also affords an understanding of the late recurrence of symptoms in children with hydromyelia who are treated with a ventricular shunt.

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.

The surgical treatment of Chiari I malformation

A retrospective study was undertaken on 133 patients with a Chiari I malformation treated within the last 16 years at the Departments of Neurosurgery at the Nordstadt Hospital Hannover, Germany, and the University of California, Los Angeles, U.S.A. Ninety-seven patients presented with symptoms related to accompanying syringomyelia and 4 with associated syringobulbia. They underwent 149 surgical procedures and were followed for a mean of 39 +/- 52 months. A decompression at the foramen magnum was performed in 124 patients, while 22 of those with syringomyelia were treated by shunting (7 syringosubarachnoid shunts, 15 syringoperitoneal or -pleural shunts), and 3 by ventriculoperitoneal shunts for hydrocephalus. Except for ventriculoperitoneal shunting, at least a short-term decrease in size of an associated syrinx was observed for all procedures in the majority of cases. However, no long-term benefit was observed for syrinx shunting operations. The best clinical long-term results were obtained with decompression of the foramen magnum in patients with (86% free of a clinical recurrence) and without syringomyelia (77% free of a clinical recurrence). We advise against syrinx shunting, a large craniectomy, and obex plugging which are associated with higher recurrence rates. Instead, surgery should consist of a small craniectomy, opening of the dura, archnoid dissection to establish normal cerebrospinal fluid (CSF) outflow from the 4th ventricle, and a fascia lata dural graft.

Syringomyelia and arachnoiditis

Five patients with chronic arachnoiditis and syringomyelia were studied. Three patients had early life meningitis and developed symptoms of syringomyelia eight, 21, and 23 years after the acute infection. One patient had a spinal dural thoracic AVM and developed a thoracic syrinx 11 years after spinal subarachnoid haemorrhage and five years after surgery on the AVM. A fifth patient had tuberculous meningitis with transient spinal cord dysfunction followed by development of a lumbar syrinx seven years later. Arachnoiditis can cause syrinx formation by obliterating the spinal vasculature causing ischaemia. Small cystic regions of myelomalacia coalesce to form cavities. In other patients, central cord ischaemia mimics syringomyelia but no cavitation is present. Scar formation with spinal block leads to altered dynamics of cerebrospinal fluid (CSF) flow and contributes to the formation of spinal cord cystic cavities.

Post-traumatic syringomyelia: a review

More than a quarter of spinal cord injured patients develop syringes and many of these patients suffer progressive neurological deficits as a result of cyst enlargement. The mechanism of initial cyst formation and progressive enlargement are unknown, although arachnoiditis and persisting cord compression with disturbance of cerebrospinal fluid flow appear to be important aetiological factors. Current treatment options include correction of bony deformity, decompression of the spinal cord, division of adhesions, and shunting. Long-term improvement occurs in fewer than half of patients treated. Imaging evidence of a reduction in syrinx size following treatment does not guarantee symptomatic resolution or even prevention of further neurological loss. A better understanding of the causal mechanisms of syringomyelia is required to develop more effective therapy.

Surgical treatment of syringomyelia based on magnetic resonance imaging criteria

The treatment of syringomyelia includes many surgical options. We report a retrospective study of 65 patients with cavitary lesions of the spinal cord in whom the results of magnetic resonance imaging were used to develop specific treatment strategies. Intramedullary cavities were classified into three general types: 1) communicating syrinxes, which occurred with hydrocephalus and were anatomically continuous with the 4th ventricle (9 patients); 2) noncommunicating syrinxes, which were separated from the 4th ventricle by a syrinx-free segment of spinal cord (42 patients); and 3) atrophic syrinxes, which occurred with myelomalacia (14 patients). Noncommunicating syrinxes were further subdivided according to type: Chiari II malformations with hydrocephalus (5 patients), Chiari I malformations without hydrocephalus (11 patients), extramedullary compressive lesions (12 patients), spinal cord trauma (6 patients), intramedullary tumors and infections (6 patients), and multiple sclerosis (2 patients). Of the 65 patients, 39 underwent surgical treatment for progressive symptoms. Syrinxes occurring with hydrocephalus were treated empirically with a ventriculoperitoneal shunt. Excellent results were achieved in 7 of 7 patients with communicating syrinxes and in all 5 patients with Chiari II malformations. Two approaches were used in the treatment of syrinxes occurring with Chiari I malformations: Posterior fossa decompression improved symptoms but did not reduce syrinx size in 2 of 3 patients. In the third patient and in 3 patients who were not treated with decompression, shunting from the syrinx to the cerebellopontine angle cistern collapsed the cavity and resolved symptoms over the interval of follow-up (average follow-up, 1.5 years). Excision of extramedullary obstructions at the rostral end of noncommunicating syrinxes resulted in collapse or disappearance of the cavity in 6 of 7 patients. The remaining patient was treated effectively by a syringocisternal shunt. In all 4 patients with posttraumatic syringomyelia, good results were achieved by a spinal or syringocisternal shunt. Syrinxes associated with intramedullary masses were managed by biopsy or excision of the causal lesion and appropriate adjunctive therapy (6 patients). Patients with atrophic syrinxes were not operated upon except to relieve symptoms referrable to the causal lesion (4 patients). Recurrent syrinxes were not encountered in the 35 surviving patients over an average follow-up of 2.5 years. It is concluded that syringomyelia is a complex pathological disorder with several mechanisms of pathogenesis that requires a number of different treatment strategies.

Preoperative MRI analysis of patients with idiopathic scoliosis: a prospective study

STUDY DESIGN

A prospective trial of preoperative MRI study in patients with "idiopathic" scoliosis.

OBJECTIVES

To investigate the prevalence of neural axis malformations and the clinical relevance of MRI in the evaluation of patients with idiopathic scoliosis undergoing surgical intervention.

SUMMARY OF BACKGROUND DATA

With the development of MRI, neural axis abnormalities such as syringomyelia or Chiari malformations are increasingly being found in patients with "idiopathic" scoliosis. The risk of neurologic complications during correction of scoliosis without prior decompression surgery for syringomyelia has been documented; however, there have been no prospective studies for identifying the risk of neurologic complications as a result of scoliosis surgery in patients with asymptomatic neural axis malformations.

METHODS

A total of 250 patients who were classified as having "idiopathic" scoliosis at first presentation and admitted for spinal surgery were evaluated. All patients were examined for neural axis abnormalities using MRI. The presence of neurologic symptoms and abnormal neurologic signs was also examined before and after surgical intervention. Neurologic complications during scoliosis surgery were reviewed in patients with neural axis abnormalities.

RESULTS

There were 44 (18%) patients (13 males and 31 females) who had neural axis abnormalities on MRI, including syringomyelia with Chiari malformations in 22 patients, syringomyelia with tonsillar ectopia in 2, Chiari malformations in 13, tonsillar ectopia in 6, and low conus medullaris in 1. On clinical examination, 44 (18%) patients had abnormal neurologic signs and 26 (7%) patients complained of headache or back pain. There were significant differences between patients with and without neural axis abnormalities regarding the age at first visit, gender, curve pattern, sagittal profile of thoracic spine, presence of neurologic deficit, and complaint of pain. Only 12 of 44 patients needed neurosurgical treatment for foramen magnum decompression before correction of scoliosis. Neurologic status temporarily worsened in 3 patients, including 2 patients with neurosurgical treatment and 1 patient without neurosurgical treatment; however, there were no permanent neurologic complications as a result of scoliosis surgery. All patients without neurologic deficits or complaints of pain did not receive neurosurgical treatment, while they had no permanent neurologic complications.

CONCLUSIONS

Foramen magnum decompression for neural axis malformations could prevent permanent neurologic complications during scoliosis surgery. There is little risk of neurologic complications in patients with "idiopathic" scoliosis whose neurologic status is normal, even if these patients have a neural axis malformation on MRI.

Toward a rational treatment of Chiari I malformation and syringomyelia

In patients with Chiari I malformation with and without associated syringomyelia, aberrant cerebrospinal fluid (CSF) dynamics and a spectrum of posterior fossa pathological findings are demonstrated. In this study, the authors test the validity of using prospective cardiac-gated phase-contrast cine-mode magnetic resonance (MR) imaging to define the malformation, delineate its pathophysiology, and assist in implementing a rational treatment plan.

Eighty-five cases were prospectively analyzed using cine MR imaging. Sixty-five patients, adults and children, with symptomatic Chiari malformation, with and without syringomyelia, were surgically treated from 1990 to 1999. All patients underwent pre- and postoperative cine MR evaluation. Ten patients were treated after a previous surgical procedure had failed. To establish CSF flow characteristics and normative CSF profiles, 20 healthy volunteers were examined.

Compared with normal volunteers, in Chiari I malformation patients with and without syringomyelia, uniformly abnormal craniocervical junction CSF flow profiles were revealed. After intradural exploration, nearly all patients with Chiari I malformation experienced clinical improvement and CSF flow profiles, paralleling those of normal volunteers, were shown. In all patients in whom treatment had failed, abnormal preoperative CSF flow profiles, which correlated with suspected physiological abnormalities and the pathological findings noted at reoperation, were demonstrated.

Symptomatic Chiari I malformation is a dynamic process characterized by the impaction of the hindbrain in an abnormal posterior fossa. This compression obstructs the normal venting of CSF in and out of the craniocervical sub-arachnoid space, throughout the cardiac cycle. Therefore, decompression or enlargement of the posterior fossa to establish normal CSF pathways should be the primary goal of surgical intervention. Aberrant CSF flow appears to be only one aspect of the pathological condition found in patients with Chiari I malformation. Arachnoid scarring in the posterior fossa and selective vulnerability of the spinal cord may also be factors in the pathogenesis and maintenance of associated syringomyelia. Phase-contrast cine MR imaging is a useful tool in defining physiological and anatomical problems in patients with Chiari I and syringomyelia, and it can help guide an appropriate primary or salvage surgical therapy.

Progressive post-traumatic cystic and non-cystic myelopathy

We describe our experience of 600 patients with progressive post-traumatic myelopathy, predominantly of the cystic type. The aetiology, clinical and radiological features and treatment are described and discussed.

Cerebrospinal fluid flow in an animal model of noncommunicating syringomyelia

OBJECTIVE

The source of fluid and the mechanism of cyst enlargement in syringomyelia are unknown. It has been demonstrated that cerebrospinal fluid (CSF) normally flows from the subarachnoid space through perivascular spaces and into the spinal cord central canal. The aim of this study was to investigate whether this flow continues during cyst formation in an animal model of syringomyelia and to determine the role of subarachnoid CSF flow in this model.

METHODS

The intraparenchymal kaolin model of noncommunicating syringomyelia was established in 78 Sprague-Dawley rats. Horseradish peroxidase was used as a tracer to study CSF flow at 1 day, 3 days, 1 week, and 6 weeks after kaolin injection. CSF flow was studied at 0, 10, and 30 minutes after horseradish peroxidase injection into the cisterna magna or thoracic subarachnoid space.

RESULTS

The central canal became occluded at the level of the kaolin injection and at one or more rostral levels. Segments of the central canal isolated between occlusions gradually dilated, and axonal retraction balls were detected in the surrounding white matter. There was a partial blockage of subarachnoid CSF flow at the site of the kaolin injection, both in a rostral-caudal direction and in a caudal-rostral direction. Horseradish peroxidase was detected at all time points, in a distinctive pattern, in perivascular spaces and the central canal. This pattern was seen even where segments of the central canal were isolated and dilated.

CONCLUSION

In this animal model, noncommunicating syringes continue to enlarge even when there is evidence that they are under high pressure. There may be an increase in pulse pressure rostral to the block of subarachnoid CSF flow, causing an increase in perivascular flow and contributing to syrinx formation. The source of fluid in noncommunicating syringomyelia may be arterial pulsation-dependent CSF flow from perivascular spaces into the central canal.

Syringomyelia in cavalier King Charles spaniels: the relationship between syrinx dimensions and pain

OBJECTIVES

This study was designed to test the hypothesis that pain associated with syringomyelia in dogs is dependent upon size and involvement of the dorsal part of the spinal cord.

METHODS

Masked observers determined syrinx dimensions and precise location within the spinal cord on magnetic resonance images of 55 cavalier King Charles spaniels with syringomyelia. After removal of masking, syrinx size and location were compared between the cohorts of dogs that exhibited pain with those that did not.

RESULTS

Maximum syrinx width was the strongest predictor of pain, scratching behaviour and scoliosis in dogs with syringomyelia. Both pain and syrinx size were positively correlated with syrinxes located in the dorsal half of the spinal cord.

CLINICAL SIGNIFICANCE

Large syrinxes associated with damage to the dorsal part of the spinal cord are associated with persistent pain suggesting that the pain behaviour expressed by this group of patients is likely to be "neuropathic pain," resulting from disordered neural processing in the damaged dorsal horn. As such it is likely that conventional analgesic medication may be ineffective.

Expansive suboccipital cranioplasty for the treatment of syringomyelia associated with Chiari malformation

In order to treat syringomyelia associated with adult type Chiari malformation, the authors developed a method of expansive suboccipital cranioplasty (ESC) that involves enlarging the small posterior fossa to obtain a sufficient flow of cerebrospinal fluid (CSF). The relative effectiveness of ESC with the obex plugged and not plugged was also examined, as well as other factors influencing the operative results. Twenty patients without arachnoid adhesion at the major cistern underwent ESC without opening the arachnoid membrane at the major cistern. After surgery, all improved with no recurrence and CSF flow study using magnetic resonance (MR) imaging showed significant improvement of the flow at the major cistern. Another 20 patients without arachnoid adhesion also underwent ESC but with obex plugging. Sixteen improved and one displayed only temporary improvement with recurrent syringomyelia due to postoperative arachnoid adhesions. The remaining three showed no change in spite of shrinkage of the syrinx on postoperative MR imaging. These three patients had displayed pre-operative symptoms over an approximately 10-year period involving almost the entire axial plain of the spinal cord, and presented a large syrinx before surgery. In 4 patients with arachnoid adhesions, all required intra-arachnoid procedures in addition to ESC. Intra-arachnoid procedures are not necessary to facilitate restoration of CSF flow in patients without arachnoid adhesions, because ESC can release the CSF flow blockage in the major cistern even without plugging of the obex. An associated arachnoid adhesion at the major cistern or a long-standing syringomyelia with irreversible damage of the spinal cord results in a poor operative prognosis. When posterior fossa surgery fails, insufficient decompression or postoperative arachnoid adhesions at the major cistern as the cause of treatment's failure should be evaluated by CSF flow studies using phase contrast MR imaging.

Terminal ventriculostomy for syringomyelia

The clinical course of 12 patients who underwent terminal ventriculostomy for syringomyelia is presented. Opening the central canal at the tip of the conus medullaris is a relatively benign procedure that improves the symptoms of syringomyelia and syringobulbia. This canal normally terminates at the tip of the conus, but in each of the 12 surgical specimens it continued into the filum terminale for distances up to 8 cm. In most cases the tip of the conus was located more caudally than normal, indicating some degree of tethering in fetal life. This belief is supported by the fact that the newborn, whose conus is tethered to a lipoma at the sacral level, may develop syringomyelia in adult life.

The acquired Chiari malformation and syringomyelia following spinal CSF drainage: a study of incidence and management

Firstly, 14 patients are described who developed either an acquired Chiari malformation (ACM) alone (7 cases) or ACM and syringomyelia (7 cases) after lumbar subarachnoid space (SAS) shunting or in one case, epidural anaesthesia with SAS penetration. Four groups are considered: 3 cases with craniofacial dysostosis and communicating hydrocephalus (CH), 4 cases with CH alone, 3 cases with pseudotumour cerebri (PTC) and a miscellaneous group (4 cases). Initial treatment was varied: resiting the shunt to ventricle or cisterna magna [6], adding an H-V valve [1], syrinx shunting [4] and posterior fossa decompression [3]. Further treatment was required in 6 cases. Secondly, incidence was examined in 87 patients with PTC initially treated either by lumbar SAS shunting [70] or cisterna magna shunting [17]. In the first sub-group, 11 cases (15.7 per cent) developed an ACM, 3 symptomatic (as above) and eight asymptomatic with 1 case also having syringomyelia whereas 1 case occurred in the second group with a questionanably symptomatic ACM. While accurate for symptomatic lesions, these figures are tentative with respect to asymptomatic lesions due to inadequate pre-treatment radiology and detailed MR follow-up. The main conclusions are, first, that the incidence of symptomatic ACM and/or syringomyelia is not high enough to warrant abandoning SAS shunting; second that asymptomatic lesions need not necessarily be treated and third, that when treatment is required, shunt resiting is the first choice.

Post-traumatic syringomyelia and post-traumatic spinal canal stenosis: a direct relationship: review of 75 patients with a spinal cord injury

This study aims to demonstrate predictive factors for post traumatic syringomyelia (PTS), and in particular to correlate the role of insufficiency of reduction of a spinal fracture with the occurrence of syringomyelia. One hundred and twenty-eight spinal cord injured patients (SCI) were studied during the years 1992 and 1993. Among them, 75 underwent a complete and reliable evaluation including: review of the initial vertebral lesion, and of the surgery report, and a radiological study of the lesion site with standard X-rays, a CT scan, and an MRI. The CT Scan included slices in sagittal reconstructions and in the axial plane at the site of injury with the calculation of a percentage of canal stenosis in the two planes of the space. An MRI was carried out with T1 and T2 weighted images, including sagittal entire cord images in addition to sagittal and axial slices centred on the site of injury. A syrinx was diagnosed in 28% of the patients. The occurrence of a syrinx is significantly correlated with spinal canal stenosis in the sagittal plane (delta D) with a P < 0.001 and in the axial plane (delta S) (P < 0.05). This present study demonstrates the major role of the insufficiency of reduction of the vertebral lesion in the genesis of a syrinx. The quality of the initial treatment of the vertebral injury is the first step in the prevention of a syrinx. The treatment of a syrinx, besides techniques of drainage, must also take into account the spinal realignment.

Experimental model of posttraumatic syringomyelia: the role of adhesive arachnoiditis in syrinx formation

An experimental model was devised to elucidate the role of spinal blockade in posttraumatic syringomyelia. Thirty-eight Japanese White rabbits, each weighing about 3 kg, were used in this study. The animals were divided into four groups: in Group 1, eight animals received traumatic injury only; in Group 2, 12 animals received traumatic injury following injection of 100 mg kaolin suspended in 1 cc normal saline solution into the subarachnoid space at the site of trauma; in Group 3, nine animals received traumatic injury following injection of 200 mg kaolin in 1 cc normal saline solution into the subarachnoid space at the site of trauma; and in Group 4, nine animals without traumatic injury received an injection of 200 mg kaolin in 1 cc normal saline solution into the subarachnoid space. The subjective criteria for syrinx formation were the presence of a definite round cyst having a smooth margin and an upper or lower extension of more than 2 cm from the injured site. Syrinx formation was seen in 12.5% (one of eight rabbits) in Group 1, 41.7% (five of 12 animals) in Group 2, 55.5% (five of nine rabbits) in Group 3 and 0% (none of nine animals) in Group 4 (p < 0.05). There was a tendency for the combined trauma/kaolin injection groups to be more prone to develop a syrinx. In the kaolin injection only group (Group 4), no animal showed a definite cyst or an extending cavity during the experimental period. The results suggest that kaolin enhances the extension of multiple small cavities that have already formed at the time of initial injury. The difference between the frequency of syrinx formation and the time of survival was statistically significant well beyond the 0.05% level. The overall difference, relating to the frequency of syrinx development, group, and duration of survival, was also statistically significant. In summary, subarachnoid block secondary to adhesive arachnoiditis is important in initiating the extension of the syringomyelia cavity.

Noncommunicating syringomyelia following occlusion of central canal in rats. Experimental model and histological findings

This report describes a new and reliable technique for producing experimental noncommunicating syringomyelia. In 30 rats, 1.2 to 1.6 microliters of kaolin was microinjected into the dorsal columns and central gray matter of the spinal cord at C-6. The inoculations caused transient neurological deficits in four animals and no deficits in 26 animals. Within 24 hours, kaolin and polymorphonuclear leukocytes entered the central canal and drained rostrally. The clearance of inflammatory products induced a proliferation of ependymal cells and periependymal fibrous astrocytes, which formed synechiae and obstructed the canal at the level of injection and at one or more levels up to C-1. In 22 animals followed for 48 hours or longer, the upper end of the central canal became acutely dilated and formed an ependyma-lined syrinx that enlarged to massive dimensions within 6 weeks. The rostral syrinxes did not communicate with the fourth ventricle and were not associated with hydrocephalus. The histological findings in acute noncommunicating syringomyelia were characterized by progressive stretching and thinning of the ependyma, elongation of intracanalicular septae, and the formation of periependymal edema. After 3 weeks, there was progressive compression of the periependymal tissues associated with stretching of axons, fragmentation of myelin sheaths, and the formation of myelin droplets. These findings and the sequence in which they evolved were identical in most respects to those occurring in acute and subacute noncommunicating hydrocephalus.

Feasibility and safety of neural tissue transplantation in patients with syringomyelia

Transplantation of fetal spinal cord (FSC) tissue has demonstrated significant potential in animal models for achieving partial anatomical and functional restoration following spinal cord injury (SCI). To determine whether this strategy can eventually be translated to humans with SCI, a pilot safety and feasibility study was initiated in patients with progressive posttraumatic syringomyelia (PPTS). A total of eight patients with PPTS have been enrolled to date, and this report presents findings for the first two patients through 18 months postoperative. The study design included detailed assessments of each subject at multiple pre- and postoperative time points. Outcome data were then compared with each subject's own baseline. The surgical protocol included detethering, cyst drainage, and implantation of 6-9-week postconception human FSC tissue. Immunosuppression with cyclosporine was initiated a few days prior to surgery and continued for 6 months postoperatively. Key outcome measures included: serial magnetic resonance imaging (MRI) exams, standardized measures of neurological impairment and functional disability, detailed pain assessment, and extensive neurophysiological testing. Through 18 months, the first two patients have been stable neurologically and the MRIs have shown evidence of solid tissue at the graft sites, without evidence of donor tissue overgrowth. Although it is still too soon to draw any firm conclusions, the findings from the initial two patients in this study suggest that intraspinal grafting of human FSC tissue is both feasible and safe.