|Year : 2000 | Volume
| Issue : 1 | Page : 81--3
Retrocerebellar arachnoid cyst with syringomyelia : a case report.
R Jain, V Sawlani, R Phadke, R Kumar
Department of Radiodiagnosis and Imaging and Neurosurgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, 226014, India., India
Department of Radiodiagnosis and Imaging and Neurosurgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, 226014, India.
Association of syringomyelia with retrocerebellar arachnoid cysts is rare. A case of 14 year old female is being reported, who presented with hydrocephalus caused by a large midline retrocerebellar infravermal arachnoid cyst leading to obstruction of the outlet foramina of the fourth ventricle. There was associated syringomyelia. The pathogenesis of syringomyelia is discussed. The need to evaluate cervical spinal cord by taking T1 weighted sagittal sections in all the patients of large posterior fossa mass lesions causing obstruction to the outlet foramina of the fourth ventricle has been stressed, in order to detect associated syringomyelia.
|How to cite this article:|
Jain R, Sawlani V, Phadke R, Kumar R. Retrocerebellar arachnoid cyst with syringomyelia : a case report. Neurol India 2000;48:81-3
|How to cite this URL:|
Jain R, Sawlani V, Phadke R, Kumar R. Retrocerebellar arachnoid cyst with syringomyelia : a case report. Neurol India [serial online] 2000 [cited 2021 May 12 ];48:81-3
Available from: https://www.neurologyindia.com/text.asp?2000/48/1/81/1468
The longitudinal cavities found within the spinal cord in syringohydromyelia can persist in isolation in the cervical, thoracic or lumbar spine or extend throughout the length of the cord. Syringohydromyelia is frequently found in association with hydrocephalus, spina bifida cystica, intramedullary tumours, the Chiari malformation and kyphoscoliosis.,,, Many authors believe that syringomyelia is caused by intermittent obstruction to the flow of CSF at the outlet foramina of the fourth ventricle. Association of syringomyelia with posterior fossa cysts is uncommon.,,
Midline posterior fossa cysts account for 10% of all cases of arachnoid cysts. They are usually situated above the vermis and present with signs of raised intracranial pressure. We recently treated a young girl of midline posterior fossa infravermial arachnoid cyst with hydrocephalus and cervical syringomyelia.
A 14 year old female presented with episodes of severe headache, vomiting and loss of consciousness for nine months. On examination her higher mental functions were normal. There was evidence of bilateral papilloedema. However, there was no sensory motor deficit. Her cranial nerve examination was normal. There was no evidence of cerebellar signs or other localizing sign. Her CT scan showed a posterior fossa cystic lesion. Magnetic resonance imaging (MRI) with spin-echo sequences in axial and sagittal planes of the head and cervical spine revealed a large midline retrocerebellar infravermal cystic lesion displacing the cerebellar hemispheres laterally and pushing the vermis upwards. No communication of the cyst with the fourth ventricle was seen, which was displaced and compressed anteriorly leading to hydrocephalus. Associated syringomyelia was found in the visualised spinal cord extending from C2 to D1 level [Figure 1]
During the hospital stay, she developed severe headache, vomiting and became drowsy. Paramedian suboccipital burr hole and drainage of about 70 cc of clear CSF like fluid was done. Subsequently, after 5 days, midline suboccipital burr hole and drainage of about 50 ml clear CSF like fluid, followed by midline suboccipital craniectomy and gross total excision of the cyst wall was done. Per-operatively sub occipital bone was thickened on the right side as compared to left side. Cyst was indenting the lateral cerebellar hemispheres, vermis and tonsil. Biopsy revealed it to be an arachnoid cyst. The patient showed marked improvement in her symptoms and had uneventful recovery.
A follow up MRI examination a week later showed gross reduction in the size of the retrocerebellar cisternal space along with significant reduction of hydrocephalus and only minimal reduction in the size of syrinx [Figure 2]. She however had no clinical features pertaining to syrinx, preoperatively or postoperatively.
The mechanism involved in the formation of syringohydromyelia is controversial. Gardener,, speculated that CSF would be diverted towards the central canal of the spinal cord if there is a blockage of formina of Luschka and Magendie. The CSF pulses originating in the choroid plexus would have a hydrodynamic or water hammer effect on the central canal, progressively dilating it and eventually resulting in hydromyelia. Williams proposed that the enlargement of the central canal results from pressure generated by engorged spinal epidural veins rather than by CSF pulses arising from the choroid plexus. The spinal subarachnoid space is compressed and a pressure wave within the compartment first moves cranially through the forman magnum and then caudally through the fourth ventricle into the central canal, as the pressure in the abdomen decreases.
Ball and Dayan have suggested that the pressure is frequently transmitted to spinal subarachnoid space by valsalva manoeuvers such as straining and coughing. However, in the presence of an obstruction to CSF flow at the foramen magnum, this CSF pressure wave might be relieved by flow through the spinal Virchow-Robin spaces into the parenchyma of the spinal cord. This fluid could collect in the central canal and create a cyst that might or might not be in continuity with the fourth ventricle. They cited numerous supportive studies with blood, isotopes and India ink in which the central canal has been demonstrated to be in continuity with the spinal subarachnoid space by these Virchow- Robin spaces.
Old field et al recently proposed a novel mechanism in the development of syringohydromyelia based on cine-MRI and intraoperative ultrasonography in 7 patients. They noted a systolic pressure wave in intracranial CSF, that is accommodated in a normal individual by the movement of fluid from basal cisterns to the spinal subarachnoid space. But the presence of a Chiari I malformation results in a piston like movement of the cerebellar tonsils that produces a systolic pressure wave in the spinal CSF. This pressure wave forces CSF into the spinal cord parenchyma along the perivascular and interstitial spaces. In the present case, the posterior fossa cyst was in a position to act like a piston and create a systolic pressure wave in the spinal subarachnoid space leading to formation of syringomyelia and was also obstructing the outlet foramina of the fourth ventricle, leading to development of hydrocephalus.
Large posterior fossa mass lesions causing pressure effects and hydrocephalus can lead to the formation of syringomyelia and the patient might not have any symptoms pertaining to the syrinx. Thus, it is important to image the cervical spinal cord by taking T1 weighted sagittal sections in all the patients of posterior fossa mass lesions presenting with symptoms due to pressure effect and hydrocephalus and not because of the syrinx. This would give vital clue to the pathogenesis of syringomyelia and can modify the treatment plan. Inadequate examination can be the reason for less number of reported cases of association of syringomyelia with posterior fossa arachnoid cysts.
Various surgical procedures are available for the treatment of syringomyelia like suboccipital craniectomy and upper cervical laminectomy, laminectomy and syringostomy, terminal ventriculostomy and percutaneous aspiration of the syrinx, decompression of the foramen magnum and cystoperitoneal shunt., The choice of the procedure depends on the anatomy of the lesion and the probable pathogenesis of the cyst formation. In our case, the midline retrocerebellar cyst was thought to obstruct the foramen magnum region and the outlet foramina of the fourth ventricle leading to syringomyelia and hydrocephalus. This could have been treated by installation of cystoperitoneal shunt or ventriculocystoperitoneal shunt as done in cases of Dandy Walker malformations. However, the risk of shunt related complications including shunt blockage is a constant problem. The CSF diversion by shunt is otherwise also not a physiological reestablishment of CSF flow. Hence the surgical excision of cysts in events of normal CSF pathway may be the appropriate modality of treatment. In the modern era of microneurosurgery, if they distal CSF pathway is intact, the surgical excision always has a better promise in reestablishing the physiological normalcy of CSF pathway, which helped in our case in resolving the hydrocephalus immediately and treating the syrinx.
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