Isolated Dorsal Midbrain Infarct: An Uncommon Cause of Pure Sensory Stroke

a Department of Neurology, University of Athens Medical School, Eginition Hospital, and b Department of Clinical Therapeutics, University of Athens Medical School, Alexandra Hospital, Athens , Greece Case Description A 60-year-old man, with a history of hypercholesterolaemia and smoking, awakened with numbness on the right part of the inner mouth and the right arm and leg. Symptoms persisted over 3 days, when he consulted the family physician, who suspected stroke and referred him to our hospital for further evaluation. On examination the patient was alert, with normal and symmetrical tendon refl exes, while both plantar responses were fl exor. A right hemihypaesthesia involving the face, trunk, arm and leg was manifest. No ataxia, dysarthria, limb weakness, or ocular motor manifestations were present. MRI of the brain was than performed on the fourth day after ictus. A hyperintense lesion of ischaemic origin located in the left dorsal portion of the midbrain was demonstrated on fl uid attenuated inversion recovery (FLAIR, fi g. 1 a), T 2 -, as well as diffusionweighted images. The infarct was obviously affecting structures localised in the dorsal (superior colliculus, periaqueductal grey matter) and the dorsolateral (medial lemsiscus and lateral spinothalamic tract) midbrain territory, supplied by the superior cerebellar artery. MR angiographic images in the time-of-fl ight technique and ultrasound of the carotid and vertebral arteries were normal. Transthoracic echocardiography, 24-hour blood pressure monitoring and Holter electrocardiographic monitoring revealed no abnormalities. Visualand auditory-evoked potentials as well as extensive blood coagulation studies were unremarkable. The patient was diagnosed as having a brainstem lacunar stroke and was discharged on aspirin and lipid-lowering medication. A slight improvement of his sensory symptoms was reported at the follow-up evaluation 6 months later, while a new MRI revealed a substantial decrease in the extent of the hyperintense lesion on the FLAIR images ( fi g. 1 b). Introduction Occlusion of branches of the thalamogeniculate arteries supplying the thalamic somatosensory nuclei is responsible for the vast majority of strokes presenting with the clinical syndrome termed by Fisher as ‘pure sensory stroke’ (isolated hemihypaesthesia or paraesthesia involving the face, trunk, arm and leg) [1] . Occasionally, pure sensory stroke can be caused by a lateral tegmental pontine or medullary infarct [2] . Brain ischaemia limited to the mesencephalon is uncommon, accounting for 0.2–2.3% of total admitted ischaemic strokes [2–5] . The anteromedial territory, supplied by the direct perforators of the basilar artery, is most frequently affected in patients with isolated midbrain infarct, whose neurological picture is dominated by oculomotor disturbances [2–5] . We report the uncommon case of a patient presenting with the clinical syndrome of pure sensory stroke due to an infarction limited to the dorsal midbrain territory.