Neuroradiology

Medullary infarction

ischaemic lesion, secondary to occlusion of the arteries emerging either from the cranial portion of the vertebral artery (anterior spinal artery) or from the origin of the posterior inferior cerebellar artery. Clinically a lateral and a medial medullary syndrome can each be recognized: the lateral syndrome is much more frequent and is characterized by impairment of pain and temperature sensation of the contralateral side (from involvement of the spinothalamic tract) associated with impairment of sensation (involvement of the fifth nerve) and Horner's syndrome (sympathetic descending fibres) to the ipsilateral side accompanied by ataxia, dizziness, nausea and vomiting (from the involvement of vestibular nuclei, olivocerebellar and spinocerebellar tracts), dysphagia and dysphonia (involvement of the ninth and tenth cranial nerves). The medial syndrome is less common and consists of paralysis of the ipsilateral half of the tongue (involvement of the twelvth cranial nerve) assicuated with motor and tactile and proprioceptive sensitive impairment to the contralateral hemisoma.

Infarctions of the cerebellum and brain stem are frequently seen with MRI, which is far superior to CT studies, the latter being impaired by artefacts emanating from the skull base. Infarctions of the brain stem are small in relation to the extent of clinical damage produced. The small lesion combined with technical problems cited above may serve to render some of these lesions undetectable by routine clinical MR. MR angiography and digital subtraction angiography may show a dissection of the vertebral artery which is frequently responsible for infarction in this area.

FS