Hemihyperaesthesia and hyperresponsiveness resembling central pain syndrome in a dog with a forebrain oligodendroglioma

A 4-year-old male Boxer was presented with neurological signs referable to a right forebrain lesion that was confirmed with computed tomography. Whils t characteristic signs of a unilateral forebrain lesion were observed, the dominant and striking finding was a right-sided hemisensory disturbance cha racterised by hyperaesthesia and hyperresponsiveness. Necropsy revealed a g elatinous mass confined to the right forebrain that was identified histolog ically as an oligodendroglioma. The lesion was centred on the internal caps ule and involved ventral frontal and temporal lobes and the ventrolateral t halamus, including lateral and medial parts of the ventrocaudal nuclear reg ion (ventrobasilar complex) of the thalamus, On clinical and neuroanatomica l grounds, the case exhibited features in common with central pain syndrome in human patients with thalamic lesions. These included a somatosensory di sorder of hyperaesthesia affecting an entire side of the head and body, beh avioural manifestations consistent with spontaneous pain and a lesion invol ving the ventrobasilar complex. Of interest, the hemisensory abnormality wa s ipsilateral to the lesion, contrasting with central pain in humans. in wh ich clinical signs are contralateral to analogous lesions. It is suggested that species-specific differences in spinal cord organisation of pain pathw ays, particularly the greater bilateral projection of nociceptive efferents to thalamic relay nuclei in carnivores, may account for this disparity. No tably, central pain is rare in human patients with brain tumours, even thos e affecting the thalamus, and this may also be the case in dogs.