Lateral medullary infarction masquerading as involvement of spinal cord

Abstract

Dear Editor, Unilateral sensory impairment below the dermatome usually suggests involvement of the spinal cord. Here, we describe a patient presenting with impaired pain and temperature sensation below the right-side Th8 dermatome due to left lateral medullary infarction. An 86-year-old woman visited our clinic presenting with numbness in her right lower leg. Her past medical history included hypertension, diabetes mellitus, dyslipidemia, hyperthyroidism, and postoperative state after the removal of a hemangioblastoma on the right cerebellum. Her consciousness was clear. Vital signs and general physical examination were normal. Neurological examination revealed deficits in pain and temperature sensation below the Th8 dermatome on the right trunk and leg (Fig. 1a). She showed dysmetria of the right arm and a wide-based gait, but both had been present for years since cerebellar tumor surgery. Motor paralysis or Horner’s syndrome was not seen. We initially suspected that she had involvement of the thoracic spinal cord. However, spinal MRI demonstrated no abnormality in the spine or spinal cord. Brain MRI revealed a small infarction in the left lateral medulla oblongata by diffusion-weighted image (Fig. 1b) and fluid attenuation inversion recovery (Fig. 1c). Magnetic resonance angiography showed an atherosclerotic stenosis at left vertebral artery (Fig. 1d), and high-echoic plaques were found in the bilateral commonand internal-carotid arteries by carotid ultrasonography. Echocardiography and 24-h EEG were normal. The patient was clinically diagnosed with atherothrombotic infarction on the basis of NINDS III classification [1]. Antiplatelet therapy was started subsequently, and the sensory impairment gradually resolved. The lateral spinothalamic tract conveys pain and temperature sensation in the contralateral body and is arranged topographically in the medulla oblongata. Afferents from caudal areas are located in the lateral portions of the tract [2] (Fig. 1e). In our case, the lesion was mostly restricted to the left lateral portion of the spinothalamic tract, affecting sensory fibers conveying superficial sensory information from the sacral, lumbar, and thoracic (to Th8) dermatomes on the right side. Accordingly, the sensory impairment was seen below the right Th8 dermatome. Reports of such patients presenting with sensory deficits in a dermatomal