Journal of Neuro-Ophthalmology, December 2006, Volume 26, Issue 4

Papilledema in the Assessment of Ventriculomegaly

To determine whether ventriculomegaly is associated with ongoing increased intracranial pressure (ICP), physicians often rely on corroborative imaging features such as altered periependymal signal, distortion of ventricular shape, subarachnoid space flattening, and an increase in ventricular size over time. In 2 patients with new headache and altered mental status, symptoms and ventriculomegaly were dismissed as long-standing and not reflective of current ICP elevation. In the first patient, ICP was considered normal because there were no corroborative imaging features of elevated ICP. In the second patient, ICP was considered normal because ventricular size was stable over a 1-year period. The diagnosis of ICP elevation was finally made by ICP monitoring after papilledema was recognized. Ventriculoperitoneal shunting rapidly resolved the papilledema and markedly improved mentation. Brain imaging may often be an unreliable guide to the presence of elevated ICP. In such patients, the finding of papilledema is a critical determinant of management.

ORIGINAL CONTRIBUTION Papilledema in the Assessment of Ventriculomegaly Iris Ben- Bassat Mizrachi, MD, Jonathan D. Trobe, MD, Stephen S. Gebarski, MD, and Hugh J. L. Garton, MD Abstract: To determine whether ventriculomegaly is associated with ongoing increased intracranial pressure ( ICP), physicians often rely on corroborative imaging features such as altered periependymal signal, distortion of ventricular shape, subarachnoid space flattening, and an increase in ventricular size over time. In 2 patients with new headache and altered mental status, symptoms and ventriculome­galy were dismissed as long- standing and not reflec­tive of current ICP elevation. In the first patient, ICP was considered normal because there were no cor­roborative imaging features of elevated ICP. In the second patient, ICP was considered normal because ventricular size was stable over a 1- year period. The diagnosis of ICP elevation was finally made by ICP monitoring after papilledema was recognized. Ven-triculoperitoneal shunting rapidly resolved the pap­illedema and markedly improved mentation. Brain imaging may often be an unreliable guide to the pres­ence of elevated ICP In such patients, the finding of papilledema is a critical determinant of management. (/ Neuro- Ophthalmol 2006; 26: 260- 263) n the presence of ventriculomegaly, corroborative imag­ing features such as altered periependymal signal, dis­tortion of ventricular shape, subarachnoid space ( SAS) flattening, and an increase in ventricular size over time are often used as determinants of elevated intracranial pressure ( ICP) ( 1,2). Although headache, vomiting, nausea, lethargy, and double vision are expected if ICP is high, these symptoms may be absent, particularly if ICP rises slowly. In such patients, ventriculomegaly is apt to be dismissed as long- standing and unrelated to elevated ICP Goldschleger Eye Institute, Chaim Sheba Medical Center, Tel Hashomer, Israel ( IBM); and Departments of Ophthalmology ( JDT), Neurology ( JDT), Radiology ( SSG), and Neurosurgery ( HJLG), University of Michigan, Ann Arbor, Michigan. Supported in part by a fellowship from the American Physician Fellowship for Medicine in Israel. Address correspondence to Iris Ben- Bassat Mizrachi, MD, Gols-chleger Eye Institute, Sheba Medical Center, Tel Hashomer, Israel 52621; E- mail: irismizrachi@ yahoo. com (" compensated"), particularly if imaging results are stable over time. We describe 2 patients who presented with headache and alterations in mental status. Family members reported that the mental status change was recent. Ventriculomegaly was present on imaging, but elevated ICP was discounted for lack of supportive imaging findings. Influenced by the lack of imaging support for increased ICP, caregivers attributed the mental status changes in the first patient to congenital mental impairment and in the second patient to a known bipolar disorder. When papilledema was later discovered, ICP monitoring disclosed markedly elevated ICP. Ventriculoperitoneal shunting resolved the papilled­ema and markedly improved mentation in both patients. These patients are presented to highlight the limitations of brain imaging alone in the diagnosis of elevated ICP and to underscore the importance of ophthalmoscopy. CASE REPORTS Case 1 A 41- year- old woman complained of persistent headache after a flu- like illness. Family members reported that her thinking had declined recently. She had a shunt placed at birth for infantile hydrocephalus associated with a Dandy- Walker malformation, but the shunt had been removed at age 1 because of malfunction. After shunt re­moval, she had had no neurologic problems except mild developmental cognitive impairment. Other than altered cognition, the emergency room neurologic examination was considered normal. Brain CT scanning showed marked dilatation of the lateral and third ventricles with slight effacement of the brain sulci ( Fig. 1A). Older neuroimaging results from another institution were not available, so it was not possible to evaluate potential changes in these imaging abnormalities. The ven­triculomegaly was judged to be chronic and unreflective of a current elevation in ICP Six weeks later, ophthalmologic examination re­vealed a visual acuity of 20/ 20 in the right eye and 20/ 70 in the left eye; the subnormal visual acuity in the left eye was attributed to known amblyopia. She had normal pupillary size and reactions, full extraocular movements with jerk 260 J Neuro- Ophthalmol, Vol. 26, No. 4, 2006 Papilledema in Ventriculomegaly J Neuro- Ophthalmol, Vol. 26, No. 4, 2006 FIG. 1. Case 1. A. At clinical presentation, a precontrast axial CT scan shows a Dandy- Walker malformation, marked ventriculomegaly, and poor sulcal definition. B. Mild optic disc edema ( papilledema) is discovered 6 weeks later. C. Six weeks after ventriculoperitoneal shunting, the CTscan shows better sulcal definition ( arrows) but minimal reduction in ventricular size. D. Six weeks after shunting, papilledema has resolved. upbeat nystagmus in upgaze and sidebeat nystagmus in horizontal gaze bilaterally, findings considered typical of congenital nystagmus. On ophthalmoscopy, mild optic disc edema was found in both eyes ( Fig. IB). When confronted, she denied having had visual symptoms or pulsatile tinnitus. The patient underwent ICP monitoring that revealed pressures ranging from 300 to 700 mm H20. At the time of ventriculoperitoneal shunt placement, CSF opening pres­sure was estimated to be 900 mm H20. Six weeks after shunting, her mental status had returned to baseline, and CT scanning showed reduced ventricular size and better sulcal definition consistent with improved cerebrospinal fluid ( CSF) dynamics ( Fig. 1C); the papilledema had re­solved ( Fig. ID). Case 2 A 54- year- old woman complained of imbalance and a reduced ability to concentrate for several weeks. When her neighbors witnessed a fall in the street, she was taken to a hospital emergency room. She had been diagnosed in the past with bipolar disorder, diabetes mellitus, systemic lupus erythematosus, and Osler- Weber- Rendu disease. Neurologic examination showed poor attention, flight of ideas, and a wide- based gait. Brain MRI showed dilatation of the lateral and third ventricles and periependymal high T2 signal, as well as numerous mass lesions consistent with cavernomas attributed to Osler- Weber- Rendu disease ( Fig. 2A). Comparison with an MRI performed 1 year earlier showed no change. Therefore, the ventriculomegaly was diagnosed as chronic and unreflective of current ICP elevation. Over the ensuing months, the patient's mental state declined to the point that she became incoherent. She was fired from her job as a hotel clerk. Six months after her initial evaluation, ophthalmologic examination disclosed marked optic disc edema ( Fig. 2B) leading immediately to inpatient ICP monitoring that demonstrated mean pressures of 300 mm H20 spiking to 500 mm H20. She denied ever having visual symptoms or pulsatile tinnitus. She promptly underwent ventriculoperitonal shunting. One month later, her flight of ideas had resolved, neurologic examination was normal, MRI showed a decrease in ventricular size ( Fig. 2C), and papilledema had disappeared ( Fig 2D). She was rehired by the hotel and has maintained her job without difficulty ever since. DISCUSSION In our two patients, the diagnosis of elevated ICP was delayed because ventriculomegaly was considered chronic and unreflective of ongoing ICP elevation. In the first patient, there were no other imaging features to corroborate elevated ICP. In the second patient, imaging results were 261 J Neuro- Ophthalmol, Vol. 26, No. 4, 2006 Mizrachi et al FIG. 2. Case 2. A. At clinical presentation, axial FLAIR MRI shows dilation of the lateral and third ventricles with apical high signal { large arrows); multiple cavernomas, part of Osler- Weber- Rendu disease, are incidental findings { small arrows). B. Marked optic disc edema ( papilledema) is discovered 6 months later. C. Four weeks after ventriculoperitoneal shunting, MRI shows reductions in ventriculomegaly and periependymal high signal. D. Four weeks after shunting, papilledema has resolved. stable over 1 year. In both patients, the diagnosis of elevated ICP was entertained only when papilledema was later detected. Passing off ventriculomegaly as " compensated" is understandable. Ventriculomegaly is, after all, a common imaging finding in patients who do not have elevated ICP The relationship between ventricular size, intraventricular pressure, and ICP is poorly understood. When ventriculo­megaly is long- standing, brain viscoelastic properties and the pressure- volume relationship may be altered such that ventricles remain expanded even when ICP is normal ( 3,4). The relationship between ventricular size and ICP is typi­cally described in terms of the intracranial compliance or elastance ( change in pressure for a given change in volume). In response to an increasing volume of CSF, patients with increased intracranial compliance typically demonstrate normal ICP, whereas those with normal or decreased compliance develop increased ICP. Ventriculomegaly may result from a number of con­ditions ( 1,2). First, there may be a loss of brain substance as occurs after trauma. Ventriculomegaly then represents " ex vacuo" dilatation, not increased ICP. Second, despite the presence of a normally functioning CSF diversion device and normal ICP, the ventricles may remain asymptomatically enlarged because the interstitial changes induced by prior CSF obstruction that was not resolved (" arrested hydrocephalus"). Third, a highly compliant brain will accommodate an increased volume of CSF without producing significantly increased ICP in normal pressure hydrocephalus. Fourth, altered CSF dynamics in a relatively non- compliant brain may result in ventriculo­megaly, sometimes with no other imaging abnormalities of high ICP yet prominent symptoms. To decide whether ICP is high, heavy reliance is often placed on neuroimaging signs such as periependymal low attenuation signal on CT and high signal on T2 MRI. When CSF is under pressure, the ependymal lining of the ventricles stretches. As a result of this stretching and a ventriculofugal pressure gradient, CSF seeps into the adjacent white matter, causing the characteristic periepen­dymal signal abnormalities ( 3,4). The ventricular dilatation also causes a decrease in size of the subarachnoid space. In our Case 1, compromise of the SAS was present but dismissed. ( It became very evident when the pre- shunt brain CT scan was compared to the post- shunt brain CT scan.) In our Case 2, periependymal high T2 signal was present but was considered part of a chronic " compensated" state because it had been present on a scan 1 year earlier. Most studies that relate ventricular size to ICP have focused on shunt- dependent patients. In a study of 100 shunt- dependent patients reviewed by radiologists for a question of shunt malfunction ( 5), 33% were false nega­tively interpreted as indicating no evidence of shunt failure. The basis for this misinterpretation was not identified. 262 © 2006 Lippincott Williams & Wilkins Papilledema in Ventriculomegaly J Neuro- Ophthalmol, Vol. 26, No. 4, 2006 The authors emphasized that radiologists should use " enlargement of ventricles over time" as a criterion for elevated ICP. However, the absence of ventricular enlarge­ment over time does not rule out raised ICP ( 6- 8), as exemplified by our Case 2. Our cases demonstrate the complexity of the diag­nosis of elevated ICP, particularly in patients whose history is not reliable and in whom the ventricles are not expected to " deflate" even when ICP is normalized. Brain imaging- even serial brain imaging- may not be enough to decide whether the brain is under pressure. In such patients, the finding of papilledema becomes a critical determinant of management. REFERENCES 1. Bradley WG Jr. Diagnostic tools in hydrocephalus. Neurosurg Clin N Am 2001; 12: 661- 84. 2. Bradley WG Jr. Hydrocephalus. 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