A 31yearold Portuguese woman MP developed a severe rightsided throbbing headache and behavioural changes over 23h. The headache was accompanied by nausea, photophobia, scintillating scotomas in the left visual field and paresthesia of the left hand. She progressively lost the ability to move the fingers of her left hand and her arm. She thought that her left upper limb had vanished and had been replaced by that of another person. She repeatedly asked her husband if there was someone else inside him. Her house and all its contents seemed foreign although she was unable to identify any concrete changes. It was as if it was raining silent and invisible drops everywhere and all the walls contained water within them.

She had suffered migraine with aura since the age of 11years but had never experienced motor deficits previously. Several relatives were also migraineurs with auras but none reported paralysis, linguistic or behavioural changes.

The neurobehavioral asomatagnosia, somatoparaphrenia, left spatial neglect and features of Capgras syndrome with reduplicative paramnesia and neurological left brachiofacial hypoaesthesia and paresis signs suggested diffuse involvement of unimodal and multimodal areas of the right hemisphere. Fundoscopy and CSF examination were normal.

Three Tesla structural brain MRI showed diffuse cortical with predominantly right posterior swelling fig 1 with neither gadolinium enhancement nor vascular changes. The differential diagnosis included cortical hypoperfusion secondary to carotid disease, vasculitis, cortical vein thrombosis, meningoencephalitis or, less commonly, conditions such as MELAS mitochondrial encephalopathy, lactic acidosis and strokelike episodes, CADASIL cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy and hemiplegic migraine HM.

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Figure 1

MRIFLAIR. Cortical hyperintensities over the frontal, parietal, temporal and occipital areas of the right hemisphere.

The diagnosis of HM was confirmed by PCR from a skin fibroblast biopsy which showed an ATP1A2 gene mutation exon 21 deletion, chromosome 1q23. ATP1A2 encodes the alpha2 subunit of NaK ATP dependent pumps.

The neurological signs persisted for 24hours, the neuropsychiatric symptoms for 4days and the headache for 7days. On day 7, a repeat MRI showed complete resolution of all cortical swelling.

This is the first documented report of a delusional misidentification syndrome occurring as a consequence of cortical changes caused by sporadic HM. Cortical swelling probably reflected local oedema, which has been reported in HM, occurring via several postulated mechanisms, including spreading depression, vasogenic processes, brain perfusion changes and ionic channel dysfunction.1,2

Ellis and Young proposed a model for Capgras syndrome based on disconnection of face identity recognition in the right parietal and temporal areas ie, on the dissociation of visual information about a familiar person or object from its affective attributes.3 However, our findings tend to suggest that diffuse cortical involvement, including frontal dysfunction, results in a failure to reject as unreal, anomalous visual and affective identity information originating in the right temporal, parietal and limbic areas.