Pituitary enlargement in patients with cerebrospinal fluid drainage due to ventricular shunt insertion: know the condition and do not mistake for adenoma

OBJECTIVE: Childhood hydrocephalus patients treated by ventriculo-peritoneal (v.-p.) shunting are sometimes referred years after this therapy for evaluation of suspicious pituitary enlargement. Since pituitary size has been shown to depend on cerebrospinal fluid (CSF) pressure, we assume this phenomenon to be caused by shunt overdrainage. Therefore, we studied pituitary size and morphology in shunted hydrocephalus patients with radiological signs of high CSF drainage. PATIENTS AND METHODS: Retrospective study of pituitary size and morphology in 15 shunted patients with non-tumoral hydrocephalus and 7 shunted hydrocephalus patients due to childhood brain tumor compared to a population mean. In five brain tumor patients also pre- and postsurgical comparisons were performed. RESULTS: Pituitary mid-sagittal size and pituitary volume were significantly higher in both hydrocephalus groups, compared to the population mean (midsagittal size t = 5.91; p < 0.001; pituitary volume, t = 3.03; p = 0.006). In patients available for pre- and postoperative comparison, there was also a significant increase in pituitary size and volume postoperatively (mean preoperative midsagittal height 2.54 ± 1.0 mm vs. 6.6 ± 0.7 mm post-surgery; mean pre-operative pituitary volume 120.5 ± 69.2 mm(3) vs. 368.9 ± 57.9 mm(3) post-surgery). CONCLUSION: Our results confirmed a significant increase in pituitary size and volume, mimicking pituitary pathology, after v.-p. shunt insertion. This phenomenon can be explained by the Monro–Kellie doctrine, stating that intracranial depletion of CSF—as caused by v.p. shunting—leads to compensatory intracranial hyperemia, especially in the venous system, with the consequence of engorged venous sinuses, most likely responsible for enlargement of the pituitary gland.