The disconnection central pain : about 2 unique cases with long term follow-up

Background & Aims

According to the formal definition, the neuropathic pain is ‘ a pain arising as a direct consequence of a lesion or disease affecting the somatosensory system ‘. However, the pain presented by the 2 patients concerned is a typical central pain syndrome, in the context of a callosal disconnection syndrome due to a ruptured anterior cerebral artery aneurysm. The various imaging and neurophysiological studies of the somato sensory pathways, repeated on several occasions, never demonstrated any lessions. The aim of this study is to describe for the first time this original central pain syndrome and to discuss its mechanisms.

Methods

1rst cases report
Following the rupture of a pericallosal artery aneurysm, a 55 years old lady presented a callosal disconnection syndrome with a typical diagonistic dyspraxia. Abnormal behaviors involved the left hand in bimanual tasks but also whole body and thoughts in more complex actions resulting in decision-making troubles. Moreover, an intensive burning pain appeared quickly afterwards, lateralized on the left with predominance over the foot and the hand. The clinical examination demonstrated a global sensory extinction on the left over the right side.

Results

Imaging studies demonstrated the corpus callosum destructive injuries without any visible lesions of the somato-sensory pathways. White matter pathways injury were analysed by diffusion tractography studies (DTI). Neurophysiological studies confirmed the extinction phenomenon without any direct disturbances on sensory conductions. Neuro-psychological explorations confirmed the split-brain syndrome and the behavioral disorders.
The symptomatology regressed little during the long evolution, but the patient adapted to it. The major problem has always been the intractable pain, temporarily relieved by IV ketamine and rTMS.
The 2nd case report is very similar, but diagonistic dyspraxia has regressed during the long evolution.

Conclusions

The occurence of a central pain without any somato sensory pathways lesion is a conundrum, as well as its onset in the context of a neglect syndrome. Based on these cases, the discussion is opened on the various mechanisms of central pain. We would assume that various callosal disconnection symptoms could result from analogous changes in higher-order cortical processing based on disruption of lateralised function as attention. Central pain could more result from a disconnection than from a circumscribed localized lesion and higher focus needs to be given on the contralateral hemispheric controls.

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