Purpose: To explain the mechanism for acquired enophthalmos after ventriculoperitoneal shunting (VPS). Design: Case series and a case-control study. Participants and Controls: Four study patients with bilateral enophthalmos after VPS and 10 control subjects. Methods: Case description of 4 study patients. Calculated orbital volumes for 2 study patients were compared with controls using the Wilcoxon rank-sum test. Main Outcome Measures: Exophthalmometry measurements and total orbital and fat volumes. Results: Patient 1 is a 25-year-old man who presented with progressive enophthalmos 3 years after VPS for traumatic intracranial bleeding. Imaging demonstrated upward expansion of the orbital roof and evidence of intracranial hypotension. The intracranial pressure (ICP) was 20 mm H 2O. The enophthalmos improved after shunt revision. Patient 2 is a 19-year-old man who presented with progressive enophthalmos 18 months after VPS for traumatic intracranial hemorrhage. Patient 3 is a 38-year-old woman who presented with bilateral enophthalmos 15 years after VPS after a ruptured aneurysm. Imaging showed orbital expansion. Patient 4 is a 16-year-old man who presented with severe enophthalmos 5 years after a VPS for aneurysm-related hemorrhage. Imaging demonstrated orbital enlargement and findings of intracranial hypotension. Intracranial pressure ranged between -200 and 0 mm H 2O. Shunt revision improved the enophthalmos. Total orbital volumes were significantly greater in the study patients than in the controls. Control subjects (5 male, 5 female, ages 2345 years) had an average right orbital volume of 24.6±3.3 cm 3 (n = 10). In comparison, the right orbital volumes of patients 1 and 3 were 32.6 and 32.1 cm 3. Similar results were found for the left orbits (23.9±2.7 cm 3 [control average] vs. 35.9 and 32.6 cm 3). In patient 1, the post-shunt volumes increased 14% (right) and 23% (left) from pre-shunt volumes. In contrast, orbital fat volume was not statistically significantly different between the control group and enophthalmic patients (right orbit control mean 7.94±3.1 cm 3 [n = 10] vs. 7.9 and 9.8 cm 3; left orbit control mean 7.88+3.1 cm 3 vs. 9.2 and 10.0 cm 3). Conclusions: Enophthalmos after VPS results primarily from chronic intracranial hypotension. Low ICP causes expansion of orbital volume with no fat atrophy. In such patients, shunt revision with a pressure-regulating valve to correct intracranial hypotension should be considered. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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