Abstract
Patients with brain lesions offer the unique opportunity to investigate mechanisms of psychosis. To our knowledge, this is the first reported case of pericallosal cerebral artery aneurysm associated with acute-onset psychosis with symptoms characteristic of schizophrenia. Aneurysms of the pericallosal cerebral artery are rare, representing only approximately 4% of all intracranial aneurysms.
The patient was a 56-year-old right-handed man with cardiovascular risk factors hypertension and smoking without any previous history of seizure disorder, head trauma or substance abuse. The patient had been in his usual state of good health until 6 months earlier, when he developed acute severe headache. On the following day he was admitted to hospital with a right leg paresis. On the same day cranial computed tomography (CT) showed hypodense frontoparietal lesions without any signs of bleeding. Magnetic resonance imaging (MRI) performed the following day showed small lesions mainly in the white matter of the left frontal and parietal lobes with involvement of the anterior cingulate, and interhemispheric frontal bleeding that was classified as subarachnoid haemorrhage graded Hunt and Hess III. Digital subtraction angiography (DSA) demonstrated two small left pericallosal artery aneurysms (both <10 mm) adjacent to the neighbouring haemorrhage. Four days after the onset of symptoms clipping of both aneurysms was performed. Six days after the clipping the hemiparesis on the right leg deteriorated. Brain MRI showed no evidence of new bleeding but there was a new infarct in the left frontal region ventral to the genu of the corpus callosum. A second DSA showed stenosis through vasospasms in the left anterior artery. In the coming weeks right leg paresis gradually improved but persisted to the same extent until discharge. In neuropsychological testing attention was assessed as being inconspicuous. Verbal memory was impaired due to difficulties in word retrieval. He had a tendency to perservate.
Six months after the aneurysm bleeding he was admitted to the emergency department of University Hospital Basel because of sudden onset of aggressiveness, incoherent speech, auditory hallucinations and delusion of persecution. The symptoms had started gradually 3 days earlier. He had no indication of suicidal intent. Cranial CT and MRI on the following day showed stable known infarcts.
Treatment with 7 mg haloperidol and 10 mg diazepam was initiated. In the coming days his delusions and aggressiveness weakened.
The main affected brain regions in the present patient are also implicated in schizophrenia. In the present case there was a marked lesion in the white matter of the frontal lobe. This falls in line with growing evidence that white matter changes play an important role in schizophrenia [1]. It is believed that one of the main factors for volume loss in the brain of schizophrenia patients could be due to reductions of neuronal connections [2]. It is hypothesized that in this disconnectivity syndrome model the frontal lobe in addition to the anterior cingulate cortex is taking centre stage [3]. This is supported by the observation that neoplasms of the white matter occurring in anterior brain areas rather than in posterior parts may cause psychosis [4]. Moreover, as seen in the present case, lesions in the parietal lobe result in ideomotor apraxia and difficulties in switching from one movement to another [5]. But psychosis remains a rare condition after damage to brain tissue and, unlike in the present patient, is usually associated with lesions of the right hemisphere.