Neurol Med Chir (Tokyo) 47, 278¿281, 2007

Disproportionately Large Communicating Fourth Ventricle With Syringomyelia —Case Report—

Naoshi HAGIHARA and Shuji SAKATA

Department of Neurosurgery, Saga Prefectural Hospital Kouseikan, Saga

Abstract A 13-year-old boy presented with syringomyelia associated with disproportionately large communicat- ing fourth ventricle (DLCFV) manifesting as symptoms attributable to and characteristic posterior fossa symptoms. Magnetic resonance imaging demonstrated remarkable dilation of the fourth ventricle and syringomyelia. Ventriculoperitoneal shunting completely resolved all symptoms as well as the ventricular and abnormalities. Pre- and postoperative cine magnetic resonance imaging revealed the change of flow signal in the area of the . We concluded that the syringomyelia could be described as enlargement of the with DLCFV.

Key words: disproportionately large communicating fourth ventricle with syringomyelia, syringomyelia, Chiari malformation, ventriculoperitoneal shunt

Introduction

Disproportionately large communicating fourth ventricle (DLCFV) was first proposed in 198016) as a subtype of hydrocephalus with dilation of all ventri- cles, disproportionately enlarged but not isolated fourth ventricle, no history of ventriculoperitoneal (VP)shunt,anddecreaseinsizeofallventriclesafter VP shunt.15) Two mechanisms have been proposed for the occurrence of DLCFV.11) Occlusion in or near the fourth ventricle outlet interacts with collision of cerebrospinal fluid (CSF) pulse waves against the obstruction to yield a ``water hammer'' effect on the fourth ventricle, or the brain stem parenchyma Fig. 1 T1-weighted magnetic resonance images around the fourth ventricle is abnormally weak to obtained 2 years before admission showing the dilated fourth ventricle but normal other CSF pressure. DLCFV is somewhat different from ventricles. the well-known clinical entity of isolated or trapped fourth ventricle because of the apparent patency of the aqueductal canal.9,11,13,15,17) Here we describe a years previously, and magnetic resonance (MR) case of DLCFV associated with syringomyelia imaging performed in another hospital demonstrat- secondary to tonsillar herniation. ed dilation of the fourth ventricle but normal other ventricles (Fig. 1). He began to suffer dizziness, Case Report headache, walking disturbance, and incontinence, and had nausea 4 weeks before admission. On A 13-year-old boy had complained of headache 2 admission, neurological examination showed nys-

Received October 16, 2006; Accepted March 30, 2007 Author's present address: N. Hagihara, M.D., Department of Neurosurgery, Koyanagi Memorial Hospital, Saga, Japan.

278 DLCFV With Syringomyelia 279 tagmus and truncal ataxia in addition to these present. symptoms. Routine biochemical analysis found no MR imaging demonstrated remarkable dilation of abnormalities. The main symptoms were attributa- the fourth ventricle and mild dilation of the other ble to hydrocephalus, but posterior fossa symptoms ventricles (Fig. 2A). Moreover, MR imaging demon- such as nystagmus and truncal ataxia were also strated tonsillar herniation, funnel-like enlargement of the entrance of central canal in the fourth ventri- cle, and syringomyelia extending from C-1 through- out the lumbar portion of spinal cord (Fig. 2B, C). Cine MR imaging revealed no CSF flow signal in the area of the foramen magnum and a small CSF flow signal without pulsation in the area of the syrinx (Fig. 3 left). Three days after admission, his con- sciousness deteriorated to drowsiness, and we de- cided to operate immediately. Immediately after a routine VP shunt operation,

Fig. 3 Preoperative cine magnetic resonance (MR) image (left) showing no cerebrospinal fluid Fig. 2 A: T1-weighted magnetic resonance (MR) (CSF) flow signal in the area of the foramen images on admission showing the remarka- magnum (arrows), and a small CSF flow bly dilated fourth ventricle, and mildly signal without pulsation in the area of the dilated other ventricles. B, C: Sagittal T1- syrinx. Postoperative cine MR image (right) weighted (B) and T2-weighted (C) MR images clearly showing CSF flow signal with pulsa- on admission showing tonsillar herniation tion in the area of the foramen magnum (arrow), funnel-like enlargement of the (arrows), but the CSF flow signal detected entrance of central canal in the fourth ven- preoperatively in the area of the syrinx was tricle, and huge syringomyelia. absent.

"

Fig. 4 A: Postoperative T1-weighted magnetic resonance (MR) im- ages demonstrating remarka- ble resolution of the dilation of all ventricles. B: Postopera-

tive sagittal T2-weighted MR image demonstrating complete resolution of tonsillar hernia- tion (arrow) and huge syrin- gomyelia.

Neurol Med Chir (Tokyo) 47, June, 2007 280 N. Hagihara et al. all symptoms were completely resolved. Postopera- space across the foramen magnum) and cause the tive MR imaging demonstrated that dilation of all pulsatile pressure waves to force CSF into the cord ventricles, tonsillar herniation, and syringomyelia through the perivascular and interstitial spaces.14) had disappeared (Fig. 4). Postoperative cine MR Moreover, communication between the fourth ven- imaging revealed CSF flow signal with pulsation tricle and the syrinx via a patent central canal at the in the area of the foramen magnum. The CSF flow is unnecessary for the development, main- signal detected preoperatively in the area of the tenance, or progression of syringomyelia, and so the syrinx was absent (Fig. 3 right). Postoperative cister- same mechanism may cause both syringomyelia nography showed no obstruction in any ventricle associated with posterior fossa tumors and syrin- (data not shown). The results of CSF cytological gomyelia associated with Chiari malformation. examination and biochemical studies were normal. Syringomyelia can be classified into the com- municating, non-communicating, and atrophic Discussion types.12) The communicating type is associated with hydrocephalus and shows enlargement of the cen- The present case of DLCFV presented with dis- tral canal with direct communication with the proportionate enlargement of the fourth ventricle fourth ventricle. The non-communicating type is with dilation of all other ventricles. VP shunt had described as enlargement of the central canal not been performed before admission. Systemic without direct communication with the fourth examination, past history, and CSF cytological ventricle. The atrophic type is described as syrinx examination found no abnormalities. All ventricles without communication with either the central were decreased in size after VP shunt, and postoper- canal or the fourth ventricle. In our case, preopera- ative cisternography revealed apparent patency of tive MR imaging revealed syringomyelia with the aqueduct. These findings fully corresponded to extension from C-1 throughout the lumbar portion of the characteristics of DLCFV. Two years before spinal cord. Preoperative cine MR imaging revealed admission, this patient presented with enlarged no CSF flow signal in the area of foramen magnum, fourth ventricle without tonsillar herniation. As the indicating that the outlet obstruction involved the fourth ventricle had been enlarged for 2 years, the fourth ventricle. After VP shunt, the huge syrin- posterior fossa gradually became tight, which led to gomyelia had completely disappeared, and postoper- tonsillar herniation. On admission, the fourth ative cine MR imaging revealed normal CSF flow ventricle was remarkably enlarged with tonsillar signalwithpulsationintheareaoftheforamen herniation associated with syringomyelia. magnum. Although MR imaging did not confirm the Syringomyelia is known to occur with acquired patency of the central canal between the fourth lesions of the foramen magnum.1,6,10) In addition, ventricle and the syrinx in our case, postoperative syringomyelia is occasionally associated with MR imaging showed that the syringomyelia disap- posterior fossa tumors and tumor-induced tonsillar peared or shrank after VP shunt without direct herniation.2,5,7,8,18) Variousmechanismsofsyrin- procedures to the syrinx or foramen magnum gomyelia secondary to tonsillar herniation due to decompression, which clearly indicated communi- posterior fossa tumors and Chiari malformation cating syringomyelia. have been proposed. Since congenital anomalies We consider secondary tonsillar herniation by at the foramen magnum were first described in DLCFV could be main cause of syringomyelia. The patients with syringomyelia associated with Chiari syringomyelia in our case was probably caused by malformations,3) it has been widely accepted that enlargement of the central canal and communica- obstruction of CSF flow at the outlet of the fourth tion with the fourth ventricle. As the fourth ventricle ventricle exerts a ``water hammer'' effect on the enlarged, the posterior fossa became tight, which led central canal, which enlarges the central canal and to tonsillar herniation as seen in patients with leads to development of syringomyelia.4) Occasional posterior fossa tumor and Chiari malformation. blockage of CSF flow at the foramen magnum leads Consequently, the CSF flow between the fourth to pressure dissociation between the ventricle and subarachnoid space around the fora- and the spinal canal through packing of the herniat- men magnum was blocked, which led to the develop- ed cerebellar tonsils.19,20) The transfer of CSF from ment of syringomyelia through the ``water hammer'' the cranial cavity to the central canal leads to the effect on the central canal. development of syringomyelia. Acquired lesions at the level of foramen magnum References can also occlude the free pulsatile movement of CSF (i.e., movement up and down the subarachnoid 1) Appleby A, Bradkey WG, Foster JB, Hankinson J,

Neurol Med Chir (Tokyo) 47, June, 2007 DLCFV With Syringomyelia 281

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