The natural history and results of surgery in 50 cases of syringomyelia

Aquaporin-4 expression and modulation in a rat model of post-traumatic syringomyelia

Aquaporin-4 (AQP4) has been implicated in post-traumatic syringomyelia (PTS), a disease characterised by the formation of fluid-filled cysts in the spinal cord. This study investigated the expression of AQP4 around a mature cyst (syrinx) and the effect of pharmacomodulation of AQP4 on syrinx size. PTS was induced in male Sprague-Dawley rats by computerized spinal cord impact and subarachnoid kaolin injection. Immunofluorescence of AQP4 was carried out on mature syrinx tissue 12 weeks post-surgery. Increased AQP4 expression corresponded to larger, multiloculated cysts (R2 = 0.94), yet no localized changes to AQP4 expression in perivascular regions or the glia limitans were present. In a separate cohort of animals, at 6 weeks post-surgery, an AQP4 agonist (AqF026), antagonist (AqB050), or vehicle was administered daily over 4 days, with MRIs performed before and after the completion of treatment. Histological analysis was performed at 12 weeks post-surgery. Syrinx volume and length were not altered with AQP4 modulation. The correlation between increased AQP4 expression with syrinx area suggests that AQP4 or the glia expressing AQP4 are recruited to regulate water movement. Given this, further investigation should examine AQP4 modulation with dose regimens at earlier time-points after PTS induction, as these may alter the course of syrinx development.

Delayed presentation of syringomyelia after retrosigmoid craniectomy and resection of vestibular schwannoma: discussion of mechanisms

We present a case of syringomyelia following retrosigmoid craniectomy and resection of vestibular schwannoma complicated by Cerebrospinal fluid (CSF) leak, multiple infections and CSF diversion procedures. We believe this is the first reported case of syrinx formation after this type of surgery. Potential mechanisms by which the syrinx may have developed are discussed.

Medical infrared thermal imaging of syringomyelia in the Cavalier King Charles Spaniel

Background

Medical infrared thermal imaging (MITI) is a non-invasive imaging modality gaining popularity in the veterinary field. An infrared camera captures emission of heat and creates a color map in the form of a thermogram. Topical heat emission is influenced by localized disease processes as a result of autonomic nervous system imbalance. The purpose of this study was to determine the utility of using thermography to identify changes in thermographic patterns associated with syringomyelia (SM) presence or absence in Cavalier King Charles Spaniels (CKCS) with Chiari-like Malformation (CLM).

Results

In CKCS with CLM, MITI was most accurate at a texture distance of 6. Optimizing imaging feature sets produced a highest accuracy of 69.9% (95% CI: 59.5–79.0%), with 81.3% sensitivity and 57.8% specificity for identifying the presence of syringomyelia.

Conclusion

Thermographic image analysis is a successful non-invasive, diagnostic test that can be used to screen for syringomyelia presence in a CKCS with CLM.

Direct-trauma model of posttraumatic syringomyelia with a computer-controlled motorized spinal cord impactor

OBJECTIVE The pathogenesis of posttraumatic syringomyelia remains enigmatic and is not adequately explained by current theories. Experimental investigations require a reproducible animal model that replicates the human condition. Current animal models are imperfect because of their low reliability, severe neurological deficits, or dissimilar mechanism of injury. The objective of this study was to develop a reproducible rodent model of posttraumatic syringomyelia using a spinal cord impactor that produces an injury that more closely mimics the human condition and does not produce severe neurological deficits. METHODS The study consisted of 2 parts. Seventy animals were studied overall: 20 in Experiment 1 and 48 in Experiment 2 after two rats with severe deficits were killed early. Experiment 1 aimed to determine the optimal force setting for inducing a cystic cavity without neurological deficits using a computer-controlled motorized spinal cord impactor. Twenty animals received an impact that ranged from 50 to 150 kDyn. Using the optimal force for producing an initial cyst determined from Experiment 1, Experiment 2 aimed to compare the progression of cavities in animals with and those without arachnoiditis induced by kaolin. Forty-eight animals were killed at 1, 3, 6, or 12 weeks after syrinx induction. Measurements of cavity size and maximum anteroposterior and lateral diameters were evaluated using light microscopy. RESULTS In Experiment 1, cavities were present in 95% of the animals. The duration of limb weakness and spinal cord cavity size correlated with the delivered force. The optimal force chosen for Experiment 2 was 75 kDyn. In Experiment 2, cavities occurred in 92% of the animals. Animals in the kaolin groups developed larger cavities and more vacuolations and enlarged perivascular spaces than those in the nonkaolin groups. CONCLUSIONS This impact model reliably produces cavities that resemble human posttraumatic syringomyelia and is suitable for further study of posttraumatic syringomyelia pathophysiology.

Natural history of untreated syringomyelia in pediatric patients

OBJECT

The natural history of syringomyelia in pediatric patients remains uncertain. Although symptomatic and operative cases of syringomyelia are well studied, there are fewer articles in the literature on the nonoperative syrinx and its clinical and radiological course. The purpose of this research was to analyze the natural history of untreated syringomyelia in pediatric patients presenting with minimal neurological symptoms.

METHODS

A review of the neurosurgery database at British Columbia's Children's Hospital identified all pediatric patients (< 18 years of age) with syringes identified on MR imaging. Patients were included in this study if they had at least 2 MR images of the spine, at least 1 year apart, while receiving nonoperative treatment. Magnetic resonance imaging was used to determine changes in the size of the syrinx over time. Clinic notes were analyzed to establish demographic and clinical features and to determine any clinical changes over time.

RESULTS

A total of 17 patients were included in the study. Symptoms at presentation were often mild and included limb numbness (3 cases), headaches (2 cases), mild sensory deficits (2 cases), mild motor deficits (3 cases), and intermittent incontinence (7 cases). The consultant neurosurgeon believed that the syrinx was not contributing to the symptoms in these 17 patients. The syrinx either remained unchanged (7 cases) or diminished in size (8 cases) in a total of 15 patients (88%). In the remaining 2 patients the authors noted an increase in syrinx size, in 1 of whom the clinical course also worsened. Both of these patients had a Chiari malformation and subsequently underwent craniocervical decompression. Overall, the mean change was -0.7 mm of maximal axial diameter (range -2.6 to +2.7 mm). Sixteen patients (94%) exhibited no worsening of symptoms over time.

CONCLUSIONS

Syringomyelia often remains stable in patients receiving nonoperative treatment. However, given that 2 (12%) of 17 syringes in this series enlarged, it is likely appropriate to include periodic imaging in the follow-up of these cases.

Pathophysiology of persistent syringomyelia after decompressive craniocervical surgery. Clinical article

OBJECT

Craniocervical decompression for Chiari malformation Type I (CM-I) and syringomyelia has been reported to fail in 10%-40% of patients. The present prospective clinical study was designed to test the hypothesis that in cases in which syringomyelia persists after surgery, craniocervical decompression relieves neither the physiological block at the foramen magnum nor the mechanism of syringomyelia progression.

METHODS

The authors prospectively evaluated and treated 16 patients with CM-I who had persistent syringomyelia despite previous craniocervical decompression. Testing before surgery included the following: 1) clinical examination; 2) evaluation of the anatomy using T1-weighted MR imaging; 3) assessment of the syrinx and CSF velocity and flow using cine phase-contrast MR imaging; and 4) appraisal of the lumbar and cervical subarachnoid pressures at rest, during a Valsalva maneuver, during jugular compression, and following the removal of CSF (CSF compliance measurement). During surgery, ultrasonography was performed to observe the motion of the cerebellar tonsils and syrinx walls; pressure measurements were obtained from the intracranial and lumbar intrathecal spaces. The surgical procedure involved enlarging the previous craniectomy and performing an expansile duraplasty with autologous pericranium. Three to 6 months after surgery, clinical examination, MR imaging, and CSF pressure recordings were repeated. Clinical examination and MR imaging studies were then repeated annually.

RESULTS

Before reexploration, patients had a decreased size of the CSF pathways and a partial blockage in CSF transmission at the foramen magnum. Cervical subarachnoid pressure and pulse pressure were abnormally elevated. During surgery, ultrasonographic imaging demonstrated active pulsation of the cerebellar tonsils, with the tonsils descending during cardiac systole and concomitant narrowing of the upper pole of the syrinx. Three months after reoperation, patency of the CSF pathways was restored and pressure transmission was improved. The flow of syrinx fluid and the diameter of the syrinx decreased after surgery in 15 of 16 patients.

CONCLUSIONS

Persistent blockage of the CSF pathways at the foramen magnum resulted in increased pulsation of the cerebellar tonsils, which acted on a partially enclosed cervical subarachnoid space to create elevated cervical CSF pressure waves, which in turn affected the external surface of the spinal cord to force CSF into the spinal cord through the Virchow-Robin spaces and to propel the syrinx fluid caudally, leading to syrinx progression. A surgical procedure that reestablished the CSF pathways at the foramen magnum reversed this pathophysiological mechanism and resolved syringomyelia. Elucidating the pathophysiology of persistent syringomyelia has implications for its primary and secondary treatment.

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.

Charcot shoulder joint associated with syringomyelia: a case report

A 36-year-old man with degenerative disease of the spine and cervical syringomyelia (syrinx) presented with new weakness and numbness in his left upper extremity. Examination revealed decreased range of motion (ROM), swelling, weakness, and diminished pinprick, vibratory, and proprioceptive sensation in the left upper extremity. Radiographic examination showed a severe destructive arthropathy; a biopsy ruled out malignancy. A culture was negative for infection, and a repeat magnetic resonance imaging (MRI) showed a patent syringo-peritoneal shunt with no change in syrinx size. He was diagnosed with a Charcot shoulder. Treatment consisted of nonsteroidal anti-inflammatory medication, passive motion exercises, and a protective sling. The patient with syringomyelia may experience sensory loss that prevents normal guarding, resulting in repetitive trauma and eventual joint destruction. Appropriate assessment, diagnostic work-up, and treatment are essential in the management of the Charcot joint. Patient education, including information on activities that may be harmful, must be included, as such knowledge may slow or prevent the impairment that comes with a Charcot joint.

Foramen Magnum Decompression with Cranioplasty for Treatment of Caudal Occipital Malformation Syndrome in Dogs

OBJECTIVES

To describe a cranioplasty procedure used in conjunction with foramen magnum decompression (FMD) for the treatment of canine caudal occipital malformation syndrome (COMS), and to evaluate the clinical outcome.

STUDY DESIGN

Prospective clinical study.

ANIMALS

Dogs (n=21) with COMS diagnosed by magnetic resonance imaging (MRI).

METHODS

After FMD, titanium screws were placed around the perimeter of the foramen magnum defect and a skull plate fashioned from titanium mesh and polymethylmethacrylate was attached to the back of the skull, using the titanium screws as anchor posts. Follow-up was obtained by direct examination by the authors, telephone interviews with owners and referring veterinarians, and a questionnaire sent to owners of surviving dogs designed to assign objective measures of response to surgical intervention. Surgical success was defined as improvement in >or=1 aspects of clinical dysfunction (e.g. scratching, pain) postoperatively. Owner-assigned pre- and postoperative quality-of-life (QOL) scores (1-5) for surviving dogs were compared using a Wilcoxon's signed rank test for paired data (P<or=.05).

RESULTS

No intraoperative complications occurred and postoperative complications were limited to transient worsening of a pre-existing head tilt and ataxia in 1 dog, and the need for oral pain medication for 1-4 weeks in 3 dogs. Seventeen dogs (81%) had clinical improvement after surgery. Although clinical signs resolved in 1 dog, it died after being hit by a car, 5 months after surgery. One dog had no change in clinical signs; this patient's clinical signs were not severe and the owners had opted for surgery primarily to prevent progression of disease. Two dogs were euthanatized; 1 because of no improvement of severe clinical signs, and 1 because of sustained recurrence of apparent head and neck pain 7 months later. One dog required a dorsal laminectomy at a second site (C1/C2 vertebral level), 2 months later. Four dogs has transient "flare-ups" of apparent head/neck pain 2-13 months later; all resolved with transient re-institution of oral analgesic therapy. Further surgery at the FMD was not needed. Based on the returned questionnaires, there was an overall significant improvement in QOL scores.

CONCLUSIONS

FMD with cranioplasty was well tolerated, with no intraoperative complications, and minor postoperative complications. Most dogs improved clinically, and none required further surgery at the original FMD site.

CLINICAL RELEVANCE

FMD with cranioplasty may be an effective surgical method of treating dogs with COMS and is well tolerated. Based on prior reports of FMD for this disorder, it appears that cranioplasty may reduce the rate of surgical failure caused by formation of compressive scar tissue at the FMD site in the short term. Results of this preliminary study support further evaluation of the cranioplasty procedure in a larger group of dogs over a more extended follow-up period.

The post-syrinx syndrome: stable central myelopathy and collapsed or absent syrinx

Among 168 cases with neurologic findings of cervicothoracic syringomyelia and MRI findings of Chiari 1 malformation and/or underdevelopment of the posterior cranial fossa, 15 patients (9.1 %) had collapsed, flat syrinxes and 14 patients (8.3 %) did not have syrinxes. Both groups of patients had clinical findings of central myelopathy that had been stable for at least 3 years. Magnetic resonance imaging detected atrophy of the cervical spinal cord in both groups and spontaneous communications between the syrinx and the subarachnoid space in 3 patients of the group with collapsed syrinxes. Analysis of these results and review of the literature suggest that patients with clinical signs of syringomyelia and Chiari 1 malformation or underdeveloped posterior fossa, but with small or absent syringomyelitic cavities, have the "postsyrinx" state as a result of spontaneous collapse of distended syrinxes.

Cordectomy for the treatment of posttraumatic syringomyelia

✓Cordectomy is an effective treatment option in patients in whom posttraumatic syringomyelia develops following complete spinal cord injuries. Since the introduction of cordectomy, numerous approaches to the surgical treatment of posttraumatic syringomyelia have been developed. These newer developments have drawn the attention of surgeons and researchers away from cordectomy. In this report, the authors encourage a reconsideration of cordectomy for the treatment of posttraumatic syringomyelia after complete spinal cord injury. They describe four patients with posttraumatic syringomyelia who were treated successfully with cordectomy and review appropriate literature, examining the effectiveness of cordectomy in the treatment of posttraumatic syringomyelia. The findings of this review indicate that neurological improvement or stabilization occurred in 88% of patients in published reports of posttraumatic syringomyelia treated with cordectomy. The indications for cordectomy as well as factors that may contribute to the procedure’s success are discussed.

Syringobulbia in a Pediatric Population

OBJECTIVE:

To better understand the presentation, management, and outcome of syringobulbia in the pediatric age group.

METHODS:

The University of Iowa pediatric neurosurgery database was searched for patients under the age of 18 with a diagnosis of syringobulbia. The patients' records were retrospectively reviewed for demographic data, chief complaint and presenting symptoms, neurological and radiographic findings, treatment, outcome, and complications. Children with open neural tube defects and Chiari II malformations were excluded.

RESULTS:

Six pediatric patients were identified as meeting inclusion criteria. The average age at time of surgery was 14.8 years. The chief complaints were vision impairment in three children and numbness, gait instability, and headache worsened with Valsalva in one patient each. Other prominent symptoms included sleep apnea and weakness. All patients showed at least one cranial nerve dysfunction. Radiographs revealed hindbrain herniation and associated syringomyelia in all cases. Two patients had scoliosis. Treatment was posterior fossa decompression with cerebellar tonsillar shrinkage, opening of foramen of Magendie, and duraplasty. Two patients also required concomitant ventral decompression. The cavity of syringobulbia communicated with syringomyelia and the fourth ventricle in most children but was distinct from the fourth ventricle. Two patients received fourth ventricle to subarachnoid shunts. Follow-up averaged 3.2 years, and all patients clinically improved after surgery. Magnetic resonance imaging documented resolution of syringobulbia in all cases, with syringomyelia improving in all cases. There was no permanent morbidity or mortality in the series.

CONCLUSION:

Syringobulbia is strongly associated with Chiari malformation and syringomyelia, and patients often present because of cranial nerve palsies. Posterior fossa decompression is a safe and effective treatment.

Foramen magnum decompression for treatment of caudal occipital malformation syndrome in dogs

A method for foramen magnum decompression (FMD) in dogs with caudal occipital malformation syndrome (COMS) and results for 16 dogs are described. In brief, a dorsal approach to the caudal portion of the occiput and arch of the atlas was made, and a high-speed drill was used to remove a portion of the occiput in the region of the foramen magnum and the dorsal aspect of C1. The meninges that were exposed were removed or marsupialized to surrounding tissues. Foramen magnum decompression was performed in 16 dogs. No intraoperative complications occurred, and postoperative complications occurred in only 2 dogs after initial surgery and in 1 of these dogs after follow-up surgery. In both dogs, postoperative complications after the initial surgery resolved without additional treatment. One dog was nonambulatory tetraparetic after follow-up surgery and died of a suspected ruptured viscus 9 days after surgery. Four dogs developed evidence of scar formation at the surgery site and required additional surgery. Overall, 14 dogs survived, 1 died, and 1 was euthanatized. Clinical signs resolved in 7 of the 14 dogs that survived, improved in 6, and did not change in 1. Results suggest that FMD may be an effective treatment for dogs with COMS, especially if performed early in the course of the disease.

Indications for magnetic resonance imaging in presumed adolescent idiopathic scoliosis

BACKGROUND

The use of magnetic resonance imaging has led to the diagnosis of abnormalities of the central nervous system associated with apparent idiopathic scoliosis. The indications for magnetic resonance imaging for presumed adolescent idiopathic scoliosis have not been established.

METHODS

One thousand, two hundred and eighty children with presumed adolescent idiopathic scoliosis were evaluated over a ten-year period. Magnetic resonance imaging of the central nervous system (brainstem and spinal cord) was performed for specific patients, on the basis of the presence of selected indicators determined from the clinical history, physical examination, and plain radiographic examination of the spine. The medical records were reviewed to determine the specific indicators, the results of the imaging studies, and the subsequent treatment.

RESULTS

Magnetic resonance imaging was ordered for 274 (21%) of the 1280 children who were evaluated. Abnormal findings were seen in twenty-seven (10%) of the 274 patients who underwent imaging, or 2% of the entire cohort. The most valuable single indicator of an abnormal finding on magnetic resonance imaging was absence of thoracic apical segment lordosis: eight of thirty-nine patients with that indicator had an abnormal finding on magnetic resonance imaging. The optimal diagnostic yield for a single category of indicators occurred when an atypical curve pattern was the only indicator: six of fifty-eight patients in whom this was the case had an abnormal finding on magnetic resonance imaging. None of the twenty children in whom pain was the only indicator category had an abnormal imaging study. The optimal diagnostic yield occurred when both an atypical curve pattern and neurological indicators were present: thirteen (25%) of fifty-three patients in whom this was the case had an abnormal finding on magnetic resonance imaging. Thirteen of the twenty-seven patients received surgical treatment for the abnormality of the central nervous system revealed by the imaging.

CONCLUSIONS

The correct use of diagnostic tests is an important component of effective medical practice. An abnormality of the central nervous system is present in approximately 10% of patients with presumed adolescent idiopathic scoliosis in whom only subtle abnormalities are identified on the basis of the clinical history, physical examination, or radiographic examination. Knowledge of the diagnostic value of the specific clinical indicators, considered individually and in combination, can help the clinician to determine more effectively when advanced imaging of the central nervous system should be performed.

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.

Syrinx size and duration of symptoms predict the pace of progressive myelopathy: retrospective analysis of 103 unoperated cases with craniocervical junction malformations and syringomyelia

OBJECTIVE

the clinical course of syringomyelia associated with craniocervical junction abnormalities is variable. About half of the unoperated patients have benign course. This is difficult to explain on the basis of the present pathogenetic theories. Therefore, to understand the mechanism of syrinx progression better, we studied the value of syrinx size, syrinx morphology, and the syrinx/spinal cord size ratio in predicting the rate of progression and the severity of myelopathy in these patients.

METHODS

103 adult patients with syringomyelia associated with Chiari 1 malformation and/or radiographic signs of underdeveloped posterior cranial fossa were clinically and MRI examined. Patients were subdivided according to the type of disease progression. Severity of neurological deficits, and MRI features (the extent of cerebellar tonsillar displacement, anteroposterior diameter of cavities, the spinal cord and cyst/cord ratio and the shape of cavities) were measured.

RESULTS

a significant relationship was found between the mid-sagittal diameter of the syrinxes and the type of disease course; patients with short duration and rapid progression had the largest diameters of cavities, whereas patients with longer duration as well as with slow rate of progression had smaller diameters (chi(2)=28.90, P<0.05; chi(2)=29.89, P<0.01; r=-0.24, P<0.05). In addition, a correlation was found between the anteroposterior diameter of the spinal cord and cyst/cord ratio and the disease duration (r=0.52, P<0.05 and r=0.48, P<0.05, respectively).

CONCLUSIONS

the initial years for the development of symptomatic syringomyelia associated with CCJ malformations are characterized by relatively rapid clinical progression accompanied with distended cavities. In the later periods of unoperated syringomyelia, some patients show delay in the progress of syrinxes accompanied with collapse of cavities, probably either due to a spontaneous formation of drainage between the syrinx and the subarachnoidal space, or due to the restoration of abnormal CSF dynamics at the CCJ level.

Shunting for syringomyelia in patients with spinal cord injuries: self-reported, long-term effects in 8 patients

OBJECTIVE

To investigate the long-term effects of shunting on neurologic outcome of syringomyelia, a complication of spinal cord injury (SCI).

DESIGN

Retrospective data collection using telephonic survey.

SETTING

University based medical center.

PARTICIPANTS

Eight of 15 patients who had shunts placed between 1976 and 1999.

INTERVENTIONS

Review of clinical records and self-reported telephone interview.

MAIN OUTCOMES MEASURES

Initial clinical presentation, recovery after shunt placement, and subsequent neurologic status were recorded. Patients were asked to rate symptomatic improvement after surgery on a 100-point analog scale; they were also asked whether they would have the surgery again.

RESULTS

Presenting symptoms were weakness in all 8 patients, pain in 5 patients, and numbness in 5 patients. After shunting, 6 patients had improved strength, all had less pain, and 2 had less numbness. Six patients experienced neurologic decline an average of 2 years after shunt placement, 3 because of shunt failure, 2 from a new syrinx, and 1 from both shunt failure and new syrinx. Two of the 3 patients who underwent second shunt placements for a new syrinx had full neurologic recovery. Six patients said they would repeat the shunting procedure if necessary, 1 was uncertain, and 1 would not.

CONCLUSION

Initial improvements noted after shunting provide long-lasting effects, even though many patients may need a second procedure. Less pain and improved strength are more significant than decreased numbness.

Incidentally identified syringomyelia associated with Chiari I malformations: is early interventional surgery necessary?

OBJECTIVE

The purpose of this study was to analyze clinical data and magnetic resonance imaging (MRI) findings for patients with asymptomatic, incidentally identified syringomyelia associated with Chiari I malformations who were monitored for more than 10 years, and to clarify the natural history of these lesions.

METHODS

The clinical records of nine patients who had not been surgically treated and were regularly subjected to neurological and MRI examinations were analyzed. In MRI studies, the axial diameter of the syrinx at the widest level, the longitudinal extent of the syrinx, and the extent of tonsillar herniation into the spinal canal were analyzed. As a control, MRI findings for 11 patients with symptomatic syringomyelia associated with Chiari I malformations who had been surgically treated were also analyzed, and these MRI parameters were statistically compared between the asymptomatic and symptomatic groups.

RESULTS

One patient underwent surgery, because of neurological changes, 7 years after the first visit. None of the remaining patients demonstrated any neurological change during the follow-up period (11.2+/-0.7 yr), and all of them have been faring well without surgery. No statistically significant differences in MRI findings between the asymptomatic and symptomatic groups were observed.

CONCLUSION

The long-term clinical courses of patients with asymptomatic, incidentally identified syringomyelia associated with Chiari I malformations were observed to be benign. MRI parameters did not provide predictable values to recommend interventional surgery. Unless changes in neurological or MRI findings are detected, early interventional surgery is not necessary.

Intraoperative measurement of spinal cord blood flow in syringomyelia

The role of spinal cord ischemia in the pathophysiology of syringomyelia remains undetermined. Previous reports in the literature suggest that shunting of syringes can improve spinal cord blood flow. In order to determine the effects of syrinx decompression on spinal cord blood flow in patients with syringomyelia, we prospectively measured regional spinal cord blood flow (RSCBF) intraoperatively pre and post shunting in patients with symptomatic syringomyelia using laser doppler flowmetry. Six patients with MRI documented syringomyelia were studied (three with Arnold Chiari I malformation and associated syrinx and three with post-traumatic syringomyelia). Surgery was performed on all patients with either a syringopleural or syringoperitoneal shunt. Laser doppler blood flow and somatosensory evoked potentials were monitored prior to myelotomy and after shunt insertion. Results indicate that there was a significant increase in RSCBF after decompression of the syrinx. This study supports the hypothesis that spinal cord ischemia is important in the pathophysiology of syringomyelia and confirms previous reports in the literature regarding RSCBF in syringomyelia.

Syringomyelia presenting as ulnar neuropathy at the elbow

OBJECTIVES

Syringomyelia may present with confusing, unilateral patterns of segmental muscle involvement and dissociated sensory loss. The objective of this study was to report a patient with Chiari malformation type 1 (CM1) and syringomyelia who had an unusual presentation suggesting ulnar neuropathy at the elbow.

RESULTS

A 24-year-old woman presented with clinical evidence of ulnar neuropathy at the elbow except that there was disproportionate abductor digiti mini (ADM) atrophy and weakness, equivocal ipsilateral abductor pollicis brevis weakness and hyporeflexia in both arms. Nerve conduction studies revealed marked amplitude reduction of the left ulnar ADM-compound muscle action potential (ADM-CMAP) with a normal first dorsal interosseous-CMAP amplitude, no focal slowing or conduction block, and a normal ulnar sensory response amplitude. Electromyography (EMG) showed multi-segmental, left C7-T1 fibrillations and chronic reinnervation changes. Magnetic resonance imaging (MRI) of the cervical spine demonstrated CM1 and syringomyelia.

CONCLUSIONS

Syringomyelia may clinically mimic ulnar neuropathy at the elbow.

Elucidating the pathophysiology of syringomyelia

OBJECT

Syringomyelia causes progressive myelopathy. Most patients with syringomyelia have a Chiari I malformation of the cerebellar tonsils. Determination of the pathophysiological mechanisms underlying the progression of syringomyelia associated with the Chiari I malformation should improve strategies to halt progression of myelopathy.

METHODS

The authors prospectively studied 20 adult patients with both Chiari I malformation and symptomatic syringomyelia. Testing before surgery included the following: clinical examination; evaluation of anatomy by using T1-weighted magnetic resonance (MR) imaging; evaluation of the syrinx and cerebrospinal fluid (CSF) velocity and flow by using phase-contrast cine MR imaging; and evaluation of lumbar and cervical subarachnoid pressure at rest, during the Valsalva maneuver, during jugular compression, and following removal of CSF (CSF compliance measurement). During surgery, cardiac-gated ultrasonography and pressure measurements were obtained from the intracranial, cervical subarachnoid, and lumbar intrathecal spaces and syrinx. Six months after surgery, clinical examinations, MR imaging studies, and CSF pressure recordings were repeated. Clinical examinations and MR imaging studies were repeated annually. For comparison, 18 healthy volunteers underwent T1-weighted MR imaging, cine MR imaging, and cervical and lumbar subarachnoid pressure testing. Compared with healthy volunteers, before surgery, the patients had decreased anteroposterior diameters of the ventral and dorsal CSF spaces at the foramen magnum. In patients, CSF velocity at the foramen magnum was increased, but CSF flow was reduced. Transmission of intracranial pressure across the foramen magnum to the spinal subarachnoid space in response to jugular compression was partially obstructed. Spinal CSF compliance was reduced, whereas cervical subarachnoid pressure and pulse pressure were increased. Syrinx fluid flowed inferiorly during systole and superiorly during diastole on cine MR imaging. At surgery, the cerebellar tonsils abruptly descended during systole and ascended during diastole, and the upper pole of the syrinx contracted in a manner synchronous with tonsillar descent and with the peak systolic cervical subarachnoid pressure wave. Following surgery, the diameter of the CSF passages at the foramen magnum increased compared with preoperative values, and the maximum flow rate of CSF across the foramen magnum during systole increased. Transmission of pressure across the foramen magnum to the spinal subarachnoid space in response to jugular compression was normal and cervical subarachnoid mean pressure and pulse pressure decreased to normal. The maximum syrinx diameter decreased on MR imaging in all patients. Cine MR imaging documented reduced velocity and flow of the syrinx fluid. Clinical symptoms and signs improved or remained stable in all patients, and the tonsils resumed a normal shape.

CONCLUSIONS

The progression of syringomyelia associated with Chiari I malformation is produced by the action of the cerebellar tonsils, which partially occlude the subarachnoid space at the foramen magnum and act as a piston on the partially enclosed spinal subarachnoid space. This creates enlarged cervical subarachnoid pressure waves that compress the spinal cord from without, not from within, and propagate syrinx fluid caudally with each heartbeat, which leads to syrinx progression. The disappearance of the abnormal shape and position of the tonsils after simple decompressive extraarachnoidal surgery suggests that the Chiari I malformation of the cerebellar tonsils is acquired, not congenital. Surgery limited to suboccipital craniectomy, C-I laminectomy, and duraplasty eliminates this mechanism and eliminates syringomyelia and its progression without the risk of more invasive procedures.

Elucidating the pathophysiology of syringomyelia

Object

Syringomyelia causes progressive myelopathy. Most patients with syringomyelia have a Chiari I malformation of the cerebellar tonsils. Determination of the pathophysiological mechanisms underlying the progression of syringomyelia associated with the Chiari I malformation should improve strategies to halt progression of myelopathy.

Methods

The authors prospectively studied 20 adult patients with both Chiari I malformation and symptomatic syringomyelia. Testing before surgery included the following: clinical examination; evaluation of anatomy by using T1-weighted magnetic resonance (MR) imaging; evaluation of the syrinx and cerebrospinal fluid (CSF) velocity and flow by using phase-contrast cine MR imaging; and evaluation of lumbar and cervical subarachnoid pressure at rest, during the Valsalva maneuver, during jugular compression, and following removal of CSF (CSF compliance measurement). During surgery, cardiac-gated ultrasonography and pressure measurements were obtained from the intracranial, cervical subarachnoid, and lumbar intrathecal spaces and syrinx. Six months after surgery, clinical examinations, MR imaging studies, and CSF pressure recordings were repeated. Clinical examinations and MR imaging studies were repeated annually. For comparison, 18 healthy volunteers underwent T1-weighted MR imaging, cine MR imaging, and cervical and lumbar subarachnoid pressure testing.

Compared with healthy volunteers, before surgery, the patients had decreased anteroposterior diameters of the ventral and dorsal CSF spaces at the foramen magnum. In patients, CSF velocity at the foramen magnum was increased, but CSF flow was reduced. Transmission of intracranial pressure across the foramen magnum to the spinal subarachnoid space in response to jugular compression was partially obstructed. Spinal CSF compliance was reduced, whereas cervical subarachnoid pressure and pulse pressure were increased. Syrinx fluid flowed inferiorly during systole and superiorly during diastole on cine MR imaging. At surgery, the cerebellar tonsils abruptly descended during systole and ascended during diastole, and the upper pole of the syrinx contracted in a manner synchronous with tonsillar descent and with the peak systolic cervical subarachnoid pressure wave. Following surgery, the diameter of the CSF passages at the foramen magnum increased compared with preoperative values, and the maximum flow rate of CSF across the foramen magnum during systole increased. Transmission of pressure across the foramen magnum to the spinal subarachnoid space in response to jugular compression was normal and cervical subarachnoid mean pressuree and pulse pressure decreased to normal. The maximum syrinx diameter decreased on MR imaging in all patients. Cine MR imaging documented reduced velocity and flow of the syrinx fluid. Clinical symptoms and signs improved or remained stable in all patients, and the tonsils resumed a normal shape.

Conclusions

The progression of syringomyelia associated with Chiari I malformation is produced by the action of the cerebellar tonsils, which partially occlude the subarachnoid space at the foramen magnum and act as a piston on the partially enclosed spinal subarachnoid space. This creates enlarged cervical subarachnoid pressure waves that compress the spinal cord from without, not from within, and propagate syrinx fluid caudally with each heartbeat, which leads to syrinx progression. The disappearance of the abnormal shape and position of the tonsils after simple decompressive extraarachnoidal surgery suggests that the Chiari I malformation of the cerebellar tonsils is acquired, not congenital. Surgery limited to suboccipital craniectomy, C-1 laminectomy, and duraplasty eliminates this mechanism and eliminates syringomyelia and its progression without the risk of more invasive procedures.

Surgical technique for cranio-cervical decompression in syringomyelia associated with Chiari type I malformation

Our purpose is to present our results with the surgical treatment of syringomyelia associated with Chiari type I malformation. Between October 1989 and October 1995, twenty-eight patients underwent a sub-occipital craniotomy and a C1 laminectomy. After dura mater opening the cerebellar tonsils were mobilised. Neither catheter, nor plugging of the obex, nor tonsillar tissue removal was performed. The dura mater was enlarged by means of a wide graft to create a new cisterna magna of adequate size. Postoperative MRI scans showed an ascent of the cerebellum of 4.3 +/- 4.8 mm (measured by the fastigium to basal line), as well as of the brainstem (mean migration of the mesencephalon-pons junction of 4.3 +/- 3.3 mm). The tonsils emigrated cranially 6.5 +/- 4.8 mm. While preoperative mean syringo-cord ratio was 66.3% +/- 13.3, post-operatively was 12.1% +/- 12.7 (p < 0.0001). A complete collapse of the syrinx was observed in 39% of the patients. Long-term improvements were obtained in 73% of the cases and 27% were unchanged. No patient got worse. We conclude that in the treatment of syringomyelia associated with Chiari I malformation an artificial cisterna magna of sufficient size must be created. This is achieved by means of an extensive sub-occipital craniotomy and C1 laminectomy, followed by dural opening. Small bone removal with limited enlargement of the posterior fossa often results in failures of treatment and recurrences. Tonsillar removal is not necessary to obtain a good reconstruction of the cisterna magna.

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.

A prospective evaluation of idiopathic left thoracic scoliosis with magnetic resonance imaging

Twenty-nine consecutive patients with idiopathic left thoracic scoliosis were prospectively studied using magnetic resonance imaging (MRI). T1-weighted sagittal and axial images were obtained on all patients from the brainstem to the tip of the conus. Two patients (7%) had a syrinx on MRI. The remaining 27 patients had normal MRIs. The prevalence of brainstem and spinal cord anomalies was much less common than reported in previous retrospective reviews.

Dysesthetic pain in patients with syringomyelia

Dysesthethic pain is a common complaint of patients with syringomyelia, traumatic paraplegia, and various myelopathic conditions. Because cavitary lesions of the spinal cord can be defined with good resolution by magnetic resonance imaging, syringomyelia provides a potential model for examining anatomic correlates of central pain. In this study, a syndrome of segmental dysesthesias, characterized by burning pain, hyperesthesia, and a variable incidence of trophic changes, was described by 51 of 137 patients (37%) with syringomyelia at the time of clinical presentation. Complete magnetic resonance scans, including axial images, demonstrated extension of the syrinx into the dorsolateral quadrant of the spinal cord on the same side and at the level of pain in 43 of 51 patients (84%). Surgical treatment of syringomyelia resulted in the relief or improvement of dysesthetic pain in 22 of 37 patients (59%), but 15 patients (41%) reported no improvement or an intensification of pain despite collapse of the syrinx. Postoperative dysesthetic pain was often a disabling complaint that responded poorly to medical therapy, including analgesics, sedatives, antiepileptics, antispasmodics, and anti-inflammatory agents. In most cases, there was a gradual improvement of symptoms, although six patients continued to complain of pain 24 to 74 months postoperatively. Prompt but transient relief was achieved in two of two patients with regional sympathetic blocks, and prolonged relief was achieved in one patient by stellate ganglionectomy. We conclude that painful dysesthesias can be caused by a disturbance of pain-modulating centers in the dorsolateral quadrant of the spinal cord and have certain causalgia-like features that respond in an unpredictable way to surgical collapse of the syrinx.

Surgical indication and results of foramen magnum decompression versus syringosubarachnoid shunting for syringomyelia associated with Chiari I malformation

Several surgical procedures have been used for the treatment of syringomyelia associated with Chiari I malformation at our institute. The purpose of this article is to evaluate the results of two major surgical procedures, foramen magnum decompression (FMD) and syringosubarachnoid (SS) shunting. The series consisted of 70 patients with syringomyelia associated with Chiari I malformation who were surgically treated. Their ages ranged from 3 to 59 years (median, 29.4 yr). FMD was performed on 33 patients, and SS shunting was performed on 37 patients. The follow-up period ranged from 6 months to 12.5 years, with a mean of 60 months. The clinical and radiological outcomes were analyzed comparing the two groups. We principally performed FMD in patients with symptoms of Chiari I malformation and/or a small syrinx. We prefer to use SS shunting in patients with large syringes. Postoperative magnetic resonance imaging demonstrated that the syrinx had collapsed or decreased in size in 94% of the patients who underwent FMD and in 100% of the patients who underwent SS shunting. Neurological improvements were observed in 82% and in 97% of the patients who underwent FMD and SS shunting, respectively. In particular, the relief of pain was more fully achieved after SS shunting than after FMD. The average time for the syrinx to collapse was 6.3 weeks after surgery in the FMD group and 1.8 weeks in the SS shunting group. These results indicate that clinical symptoms and radiological findings improved much more quickly in the SS shunting group than in the FMD group.(ABSTRACT TRUNCATED AT 250 WORDS)

Birth injury as a causative factor of syringomyelia with Chiari type I deformity

The epidemiology of syringomyelia with Chiari type I deformity was investigated with particular reference to perinatal problems. All subjects in our study were born by vaginal delivery and had a high incidence of perinatal accidents (abnormal presentations, birth injuries, and neonatal asphyxia). This study suggests that these may be strong causative factors for syringomyelia associated with Chiari type I deformity.

Pediatric syringomyelia

Syringomyelia was first recognized as a disease process some 400 years ago. The process of cystic dilation of the spinal cord is unpredictable and may result in a delay of many decades before the symptoms and signs of neurologic and orthopedic changes become apparent and commensurate with the observed cystic changes within the spinal cord. The syringomyelic process is usually associated with trauma, tumor, or congenital abnormalities at the craniocervical junction or along the spinal neuraxis. Several theories have been proposed as to processes involved in the development of spinal cyst formation, although none are completely compatible with the observed clinical pathology of syrinx development. Magnetic resonance imaging has markedly improved our ability to study the anatomy and natural history of syrinx formation, but to date, our understanding of the process remains imprecise. In view of the limited understanding of the pathophysiology of this disease process, it is not surprising that a variety of treatment regimens have been proposed and their efficacy remains difficult to fully evaluate.

Familial syringomyelia: case report and review of the literature

We report a case of familial syringomyelia consisting of two sisters, one of whom had syringomyelia and Chiari type I malformation and the other, who had died 5 years earlier, had syringomyelia and Klippel-Feil syndrome. Although syringomyelia is uncommon and familial cases rare, they continue to be reported from time to time. Review of the literature certainly suggests that genetic factors play a part in the etiopathogenesis of syringomyelia related to abnormalities of the hindbrain structures, although the number of cases is too small for the exact nature of transmission be established.

Foraminal syringomyelia: suggestion for a grading system

The standard treatment of foraminal syringomyelia includes foramen magnum decompression and duraplasty. Improvement or stabilization of the disease are achieved in most of cases. However, at least one third of patients are reported to receive little or no benefit. In this paper we retrospectively reviewed a series of 40 consecutive foramen magnum decompressions in order to identify the possible pre-operative outcome predictors. Based on clinical evolution, neurological impairment and radiological features, a scale of severity was fixed and retrospectively tested. A pre-operative score was obtained for each patient and was correlated with the surgical results. Then a four level grading system was derived. All grade I and grade II patients achieved good results (improvement or stabilization), whereas grade III patients showed intermediate behaviour and grade IV invariably worsened. On this basis, surgical results of foramen magnum decompression might be further improved provided that a careful pre-operative selection is made.