Manic Episode after Ventricular-Peritoneal Shunt Replacement in a Patient with Radiation-Induced Hydrocephalus: The Role of Lifetime Subthreshold Bipolar Features

We present a case report of a woman hospitalized for a ventricular-peritoneal shunting replacement, who developed a manic episode with psychotic symptoms after hydrocephalus resolution. We have no knowledge of cases of manic episodes due to hydrocephalus resolution by ventricular-peritoneal shunt replacement, although previous case reports have suggested that hydrocephalus might induce rapid-onset affective episodes or mood cycles. The patient’s history revealed the lifetime presence of signs and features belonging to the subthreshold bipolar spectrum, in absence of previous full-blown episodes of a bipolar disorder. Our hypothesis is that such lifetime sub-threshold bipolar features represented precursors of the subsequent full-blown manic episode, triggered by an upregulated binding of striatum D2 receptors after the ventricular-peritoneal shunt replacement. 1. Introduction Neuropsychiatric manifestations, although uncommon, have been described in association with hydrocephalus (a condition caused by obstruction in drainage, decreased absorption or excess production of cerebrospinal fluid). Normal Pressure Hydrocephalus (NPH) may present with its classic progressive triad (abnormal gait, ataxic/apractic dementia and urinary incontinence) [1], as paranoid psychosis [2, 3] or as a mood disorder, such as depressive episodes, manic episodes [4–6], or mood cycling [7, 8]. As far as we know, there is no knowledge of mood episodes with the onset after hydrocephalus resolution. We present the case of a woman hospitalized for a ventricular-peritoneal shunt replacement after a radiation-induced hydrocephalus, who developed a manic episode with psychotic symptoms when hydrocephalus remitted. The patient was treated with antipsychotics and completely recovered. Apparently no previous mood episodes had been manifested in her lifetime history. However, the information collected during hospitalization revealed a lifetime history characterized by several indicators of a bipolar spectrum diathesis. We hypothesized that the ventricular-peritoneal shunting might be associated with an increased dopaminergic tone and that this condition was able to trigger the manic episode in a patient with a lifetime history of subthreshold bipolar manifestations. This hypothesis derived from two recent positron emission tomography studies that found a reduced binding of striatum D2 receptors in normal pressure hydrocephalus [9] and an upregulated binding after the ventricular-peritoneal shunting [10]. Moreover, both studies showed that changes in striatum D2 receptors were correlated