Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 59, Num. 3, 2011, pp. 467-469

Neurology India, Vol. 59, No. 3, May-June, 2011, pp. 467-469

Letter to Editor

Cerebellar distortion after a cystoperitoneal shunt for arachnoid cyst

Suk-Won Ahn¹, Kyoung-Tae Kim², Hae-Won Shin¹, Young-Chul Youn¹, Kwang-Yeol Park¹, Oh-Sang Kwon¹, Yong-Sook Park³

¹ Department of Neurology, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul, Korea
² Department of Neurosurgery, Kyungpook National University Hospital, Daegu, Korea
³ Department of Neurosurgery, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul, Korea

Correspondence Address: Suk-Won Ahn Department of Neurology, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul Korea cuttage@cau.ac.kr

Date of Submission: 01-Feb-2011
Date of Decision: 01-Apr-2011
Date of Acceptance: 07-Apr-2011

Code Number: ni11134

PMID: 21743187

DOI: 10.4103/0028-3886.82739

Sir,

Arachnoid cysts account for 1% of all the intracranial mass lesions and 10-30% of them are posterior fossa in location. ^[1],[2] Posterior fossa arachnoid cysts are often asymptomatic and may not grow, when symptomatic the clinical presentations include: ataxia, dizziness, tinnitus, hearing loss, headache, seizures, and tremors.^[1],[2],[3] The clinical symptoms result from hydrocephalus and compression of the adjacent structures. Treatment of symptomatic arachnoid cysts includes serial cyst fenestration, stereotactic puncture, endoscopic cyst fenestration, cystoperitoneal shunt, cyst marsupialization into the subarachnoid space, and complete or partial resection of the cyst wall. ^{[3],[4],[5],[6]} However, the natural course of arachnoid cysts remains to be elucidated and surgical treatment remains controversial.

A 31-year-old woman presented with intractable dizziness, nausea, and gait disturbance of 1-year duration. Her past medical history indicated chronic headaches since her early twenties and the headache description was bilateral insidious-onset severe hemicranial accompanied by nausea and vomiting without photophobia and phonophobia, lasting for a few days without fully remitting. Two years before she visited our clinic, her headaches had become more intense, and their duration had increased. She had brain magnetic resonance imaging (MRI) at other hospital which revealed a large arachnoid cyst involving the posterior fossa [Figure - 1]a. Although no neurological abnormalities besides the headache were noted, she had consented to surgery and undergone a fenestration surgery without relief of the headache. She had subsequently undergone cystoperitoneal shunt operation of the arachnoid cyst at the other hospital. One year after the shunt operation, the patient started complaining of severe dizziness and gait disturbance. For 1 year, she visited several hospitals for treatment, but the symptoms worsened over time. Neurological examination on admission to our hospital revealed ataxia in the right upper and lower extremities and gait ataxia. She could not sit up owing to the severe dizziness and could not help but lying down almost all day. Repeat brain MRI showed severe distortion of the right cerebellum, cerebellar peduncle and herniation of the cerebellar vermis into the cyst with a reduction in the size of the arachnoid cyst in the posterior fossa [Figure - 1]b and c. Cerebellar distortion and vermian herniation were suspected to be the cause of the dizziness and gait disturbance. The patient was treated with various medications, but none could cure the dizziness. Subsequently she underwent ligation of the shunt catheter at the level of her neck, and the dizziness and gait disturbance completely disappeared postoperatively.

Intracranial arachnoid cysts are intra-arachnoid collections of cerebrospinal fluid. They are regarded as a developmental abnormality of the arachnoid, originating from splitting or duplication of this membrane. ^[1],[2] The management of arachnoid cysts is somewhat controversial, even though many operative procedures have been recommended. ^[1],[2],[3] Undoubtedly, surgical treatment is necessary for patients with increased intracranial pressure, compression on the surrounding brain structures, cyst rupture, intracystic or subdural hemorrhage and the corresponding clinical symptoms. However, conservative management can be considered for asymptomatic patients or for those complaining of mild symptoms. In our case, the patient had complained of chronic daily headaches, indicating that the retrocerebellar arachnoid cyst with increased intracranial pressure was a cause of the headache.^[3],[5] Thus, the arachnoid cyst in our patient warrants surgical treatment, however unfortunately, surgical procedure resulted in an unexpected complication of the distortion in cerebellum, cerebellar peduncle and vermis. To our knowledge, this is the first reported case of such a complication occurring in association with a cytoperitoneal shunt operation of a retrocerebellar arachnoid cyst. We hypothesize that surgical drainage of the cyst in the posterior fossa led to distortion of the cerebellum and cerebellar peduncle resulting in intractable dizziness and gait dsturbance. The vestibular nervous system in part projects directly to the phylogenetically oldest parts of the cerebellum-namely, the flocculus, nodulus, ventral uvula, and the ventral paraflocculus-on its way directly through the vestibular nucleus. The stretching distortion of cerebellum in our patient might result in functional impairment of vestibular system, which might result in dizziness and gait disturbance. ^[7] However, unfortunately, the etiology of asymmetrical drainage is not clear, and there has been no previous report on asymmetrical drainage similar to our patient. We could just assume that this phenomenon might result from adhesion between right cerebellum and arachnoid cyst during surgical procedure. However, further studies on causes of asymmetrical drainage are needed. In conclusion, cystoperitoneal shunt operation for arachnoid cysts may result in intractable complications, as in our patient. And, in such case, ligation of the shunt catheter at the level of the neck could recover cerebellar distortion and neurological symptoms.

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