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Show Relapsing Dorsal Midbrain Syndrome Following Interventions for Hydrocephalus in Aqueductal Stenosis Alexandra O. Apkarian, MD, Hugh J. L. Garton, MD, Jeffrey Wesolowski, MD, Jonathan D. Trobe, MD Abstract: Dorsal midbrain syndrome (DMS) is a recognized clinical manifestation of increased intracranial pressure (ICP) associated with ventricular enlargement, especially in shunt malfunction, but the mechanism by which DMS occurs in this setting is unsettled. We report a patient with triventriculomegaly attributed to aqueductal narrowing by a tectal mass who went through 2 cycles of developing and resolving DMS promptly after undergoing interventions that altered the size of the posterior third ventricle and proximal aqueduct but probably did not markedly alter ICP. This case provides additional evidence that DMS in this setting is caused by deformation of the dorsal midbrain region produced by rapid expansion of the posterior third ventricle or proximal aqueduct. Journal of Neuro-Ophthalmology 2012;32:124-127 doi: 10.1097/WNO.0b013e318242a0de © 2012 by North American Neuro-Ophthalmology Society The dorsal midbrain syndrome (DMS, Parinaud syn-drome, or pretectal syndrome) is characterized by upgaze paresis, convergence-retraction nystagmus, pupillary light-near dissociation, lid retraction, and skew deviation (1,2). It may be seen in patients with intraventricular obstructive hydrocephalus (3), but the mechanism for the development of the DMS in this setting is unsettled. Increased intracranial pressure (ICP) alone is an unlikely explanation (4), given that the DMS does not develop when increased ICP exists without hydrocephalus. One possible explanation is a conformational change of the dorsal mid-brain, as might occur with dilation of the posterior third ventricle or proximal Sylvian aqueduct. But imaging evi-dence of such a conformational change in conjunction with development of a DMS has been sparse (5,6). Because hydrocephalus is usually associated with an increase in ICP, it has been difficult to isolate a brain conformational change as the mechanism of the DMS in this setting. We present a patient with shunted hydrocephalus who repeatedly developed DMS immediately after surgical interventions that enlarged the ventricles but probably did not alter ICP. We offer this case as support for the theory that a rapid enlargement of the posterior portion of the third ventricle or proximal aqueduct with attendant deformation of the dorsal midbrain is the mechanism of the DMS in hydrocephalus. CASE REPORT A 9-year-old girl developed transient loss of consciousness after a 6-month period of morning headaches, unsteady gait, urinary incontinence, and poor school performance. Brain MRI showed enlargement of the lateral and third ventricles and high T2/FLAIR signal in the dorsal midbrain consistent with a low-grade glioma (Fig. 1). The midbrain was flattened, and the tectum was displaced posteriorly and superiorly with enlargement of the proximal Sylvian aque-duct (Fig. 2A). The patient's head size measured 60 cm (.95th percen-tile). She had no visual symptoms. Ophthalmologic exam-ination showed a visual acuity of 20/20, right eye, and 20/40, left eye, a left relative afferent pupillary defect (RAPD), a comitant intermittent exotropia of 25 prism diopters, and pale optic discs bilaterally. The RAPD and pale optic discs were attributed to the damage to the optic nerves from previous papilledema caused by increased ICP. She was unable to cooperate for perimetric testing. There Departments of Ophthalmology and Visual Sciences (Kellogg Eye Center) (AOA, JDT), Neurology (JDT), Neurosurgery (HJLG, JDT), and Radiology (Neuroradiology) (JW), University of Michigan Med-ical Center, Ann Arbor, Michigan. The authors report no conflicts of interest. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the full text and PDF versions of this article on the journal's Web site (www.jneuro-ophthalmology.com). Address correspondence to Jonathan D. Trobe, MD, Kellogg Eye Center, 1000 Wall Street, Ann Arbor, MI 49105; E-mail: jdtrobe@ umich.edu 124 Apkarian et al: J Neuro-Ophthalmol 2012; 32: 124-127 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. were no clinical features of a DMS. Neurological examina-tion was notable for an inability to perform tandem gait. The lack of a prepontine subarachnoid space and the proximity of the basilar artery to the floor of the third ventricle on the preoperative MRI and on intraoperative endoscopy precluded performance of a third ventriculos-tomy. Instead, she underwent placement of a right frontal ventriculoperitoneal (VP) shunt with an Orbis Sigma II valve (Integra Lifesciences, Plainsboro, NJ). The septum pellucidum was noted to have multiple wide fenestrations consistent with longstanding hydrocephalus. At Day 17 after shunt placement, ophthalmologic exam-ination showed no DMS. Incontinence, gait disturbance, and headache had largely resolved. Brain MRI showed decreased ventricular size and disappearance of the midbrain deformity but also bilateral subdural effusions attributed to ventricular decompression and a failure of the brain parenchyma to expand into the available intracranial space. At Day 56 after shunt placement, there was still no DMS, and brain MRI continued to demonstrate reduced ventricular size without midbrain deformity (Fig. 2B). The subdural fluid collections had enlarged prompting placement of a sub-dural shunt and replacement of the VP shunt valve with a Strata adjustable valve (Medtronic, La Jolla, CA). At both of these surgical procedures, the ICP was normal. On examination at Day 64 after original shunt place-ment (and 12 days after placement of the subdural shunt), the patient reported double vision. Ophthalmologic exam-ination disclosed that pupils measured 6 mm in dim illumination and constricted minimally to light and near. Lateral gaze and downgaze were intact, but upgaze was absent. Convergence-retraction eye movements were present on attempted upgaze. (See Video 1, Supplemental Digital Content 1, http://links.lww.com/WNO/A27:DMS present. The patient's eyes are downwardly deviated. She is unable to make upward saccades. To a downgoing optokinetic stimulus, she displays retraction of the eyes.) These findings were consistent with DMS. While brain MRI showed that the subdural fluid collections were considerably smaller, the lateral and third ventricles had enlarged, the posterior tectum was again displaced posteriorly and superiorly, the midbrain was flattened, and the proximal aqueduct dilated (Fig. 2C). With the goal of reversing the DMS, the adjustable shunt valve was reset to offer less resistance to cerebrospinal fluid (CSF) drainage. This maneuver failed to reverse the DMS, so that the ventricular shunt was externalized and the shunt valve was removed. No evidence of hardware failure was identified. Over the ensuing 2 weeks, attempts were made to achieve a reduction in ventricular size by increasing ventricular drainage. The catheter system was eventually set to siphon fluid from the ventricular system at a pressure of 20 cm below the tragus of the ear. A gentle cervical tourniquet was used to increase jugular venous resistance and interstitial brain pressure. The patient's DMS gradually improved, and the ventricular system decreased in size with some return of the subdural fluid collections. On Day 78, a new shunt system was inserted with a Codman Medos valve set at 30 mm pressure. Ophthal-mologic examination disclosed that the patient's DMS had largely resolved. (See Video 2, Supplemental Digital Con-tent 2, http://links.lww.com/WNO/A28:DMS not present. The patient's eyes are no longer downwardly deviated. She makes normal horizontal and downward saccades. Upward saccades remain slightly impaired but are much improved over Video 1, Supplemental Digital Content 1, http://links.lww.com/WNO/A27.) Brain MRI showed that the ventricular system had become smaller and that the tectal displacement and midbrain flattening had decreased (Fig. 2D). On Day 106, with the adjustable shunt valve having been progressively increased to 180 mm water pressure to limit subdural fluid collections, brain MRI showed that the ventricular system had modestly dilated and that the right subdural effusion had enlarged with associated new hem-orrhage. In addition, the right subdural catheter was noted to be disconnected from its distal drainage tubing. Because of the fresh subdural hemorrhage and the lack of an effective drainage mechanism, the right parietal subdural catheter was replaced. Intraoperatively, the subdural fluid was noted to be FIG. 1. Axial FLAIR MRI shows high signal in the dorsal midbrain (arrow) presumed to be a low-grade glioma re-sponsible for narrowing the aqueduct and impeding cerebrospinal fluid flow. Also seen are dilated third and lateral ventricles with high signal around them representing transependymal CSF flow. Apkarian et al: J Neuro-Ophthalmol 2012; 32: 124-127 125 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. under low pressure. The ventricular shunt was not manipulated operatively. That evening, the patient reported diplopia and the DMS had worsened. (See Video 3, Supplemental Digital Content 3, http://links.lww.com/WNO/A29:DMS present. The patient's eyes are not downwardly deviated but she is unable to make upward saccades. To a downgoing optokinetic stimulus, she again displays slight retraction of the eyes.) Brain MRI revealed that the ventricular system had redilated with return of the abnormal morphology of the posterior third ventricle (Fig. 2E). In response to these findings, the ventricular shunt valve setting was lowered to 30 mm H2O to reduce resistance to FIG. 2. A-F. Chronological summary of appearance and disappearance of DMS associated with presence of midbrain deformity detected on MRI. Note the change in appearance of the proximal portion of the Sylvian aqueduct (arrows). 126 Apkarian et al: J Neuro-Ophthalmol 2012; 32: 124-127 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. CSF drainage. The cervical tourniquet was reapplied to increase ICP so that the ventricles would shrink. Within hours, the diplopia had disappeared and the DMS had largely resolved. (See Video 4, Supplemental Digital Content 4, http://links.lww.com/WNO/A30:DMS not present. The patient has regained the ability to make pursuit and saccadic eye movements in all directions, including the vertical plane.) Brain MRI showed resolution of the conformational changes in the posterior third ventricle and reduced ventriculomegaly (Fig. 2F). Over the next month, the shunt valve was gradually adjusted upward to 60 mm in order to limit the re-expansion of the patient's subdural hematoma. On Day 140, there was still no DMS and no ventriculomegaly or conformational changes of the dorsal midbrain on brain MRI. DISCUSSION We have described a patient who developed a DMS twice within hours to days of surgical interventions that led to enlargement of the ventricles and conformational changes of the proximal aqueduct. On both occasions, the DMS developed promptly after drainage of the subdural fluid collections that presumably resulted in a reduction, not an elevation, in ICP but in ventricular enlargement and deformation of the midbrain. This midbrain deformity was likely driven by a relative increase in pressure across the ventricular wall due to a drop in the extra-axial pressure as the subdural fluid drained through the shunt. Such a trans-mural gradient was presumably acting on a highly compli-ant cerebral cortex, as demonstrated by the need for aggressive negative pressure drainage and a cervical tourni-quet to resolve the ventriculomegaly and the DMS. We believe this to be only the third report to demon-strate a change in the configuration of the dorsal midbrain after manipulations of CSF drainage. Lerner et al (5) per-formed air ventriculography before and after placement of a Torkildsen ventriculocisternostomy in a 9-year-old girl presenting with headache, vomiting, and clumsiness. Pre-operatively, she had papilledema and a DMS, and imaging disclosed that the dorsal midbrain was compressed between an expanded third ventricular suprapineal recess and a fun-nel- shaped enlargement of the proximal aqueduct. Within days of shunt placement, all neurologic findings had abated and pneumoencephalography was normal. In a report of 28 patients presenting with DMS related to shunt malfunction in obstructive hydrocephalus of various causes, Cinalli et al (6) displayed the MRI features from 3 patients (Cases 6, 18, and 27) before and after they underwent endoscopic third ventriculostomy. Before the procedure, the images showed ballooning of the posterior third ventricle into the suprapineal recess with deformation of the dorsal midbrain or an increase in its T2 signal intensity. These changes disappeared within days of third ventriculostomy. The authors proposed that changes in the transtentorial pressure gradient had caused the DMS. We corroborate the imaging findings of these publica-tions. Our report differs in that it shows 2 cycles of development and regression of these imaging abnormalities in conjunction with the development and regression of the DMS. Our patient's macrocephaly and fenestrated septum pellucidum are evidence that her hydrocephalus was long-standing. Prior to the first shunt placement, she had massive triventriculomegaly and deformation of the midbrain yet did not display a DMS. We explain these phenomena by suggesting that her brain adapted to slow expansion of the ventricles without clinical dysfunction. In contrast, drainage of the subdural fluid led to rapid expansion of the ventricles and conformational changes in the midbrain to which the brain could not adapt, so that a DMS resulted. This case exemplifies how the brain may tolerate a static or slowly progressive deformation but not a rapid one. We do not know whether the tectal glioma increased the patient's vul-nerability in the face of such a perturbation. REFERENCES 1. Keane JR. The pretectal syndrome: 206 patients. Neurology. 1990;40:684-690. 2. Baloh RW, Furman JM, Yee RD. Dorsal midbrain syndrome: clinical and oculographic findings. Neurology. 1985;35: 54-60. 3. Chattha AS, Delong GR. Sylvian aqueduct syndrome as a sign of acute obstructive hydrocephalus in children. J Neurol Neurosurg Psychiatry. 1975;38:288-296. 4. Chou SY, Digre KB. Neuro-ophthalmic complications of raised intracranial pressure, hydrocephalus, and shunt malfunction. Neurosurg Clin N Am. 1999;10:587-608. 5. Lerner MA, Kosary IZ, Cohen BE. Parinaud's syndrome in aqueduct stenosis: its mechanism and ventriculographic features. Br J Radiol. 1969;42:310-312. 6. Cinalli G, Sainte-Rose C, Simon I, Squoros S. Sylvian aqueduct syndrome and global rostral midbrain dysfunction associated with shunt malfunction. J Neurosurg. 1999;90:227-236. Apkarian et al: J Neuro-Ophthalmol 2012; 32: 124-127 127 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. |
