The Corpus Callosum is the largest tract of white matter fibres within the brain, connecting the left and right hemispheres as an anatomical mediator of inter-hemispheric transfer. Nasrallah proposed that first rank Schneiderian symptoms in schizophrenia could be due to a state of impaired hemispheric awareness, in which each hemisphere regards the input from the other as non-self, or alien information from an external source.1 Lesions of this tract could therefore present with such features in terms of sensory and emotion processing, in addition to other neurological and neuropsychiatric phenomena.
To describe a case of a 27 year old female patient who presented with neuropsychiatric symptoms (including maniform psychosis, hallucinations and passivity phenomena) after developing severe radionecrrosis of the corpus callosum following cyber-knife radiotherapy to a solitary melanoma metastasis of the brain.
A detailed review of the hard copy and electronic medical record and relevant neuro-imaging was undertaken with the permission of the patient and family. Structured liaison psychiatry and neurological assessments were conducted as part of the initial and subsequent reviews.
The neurological and neuropsychiatric phenomena observed in this patient were felt to be directly attributable to the involvement of the corpus callosum, resulting in an organic “disconnection” syndrome. This understanding was utilized to guide psychoeducation of the patient and family and to inform further care including prescription of psychotropic medications, provision of care workers to support independence, and the rationale for further treatment with bevacizumab.
The authors propose a potential aetiology whereby the location of the organic radionecrosis lesion involving the corpus callosum, and the function of this brain region in sensory integration and processing, contributed to the clinical picture of neuropsychiatric and neurological phenomena observed.
Nasrallah HA: The unintegrated right cerebral hemispheric consciousness as alien intruder: a possible mechanism for Schneiderian delusions in Schizophrenia. Compr Psychiatry 1985;26:273-282