Restricted Acral Sensory Syndrome as a Sentinel of Major Medullary Infarction - A Window to Act

INTRODUCTION Infarcts in the brainstem have been reported to cause pure or predominantly sensory stroke, most common with Pontine and Midbrain infarctions, only second to thalamic lesions. Medial medullary syndrome as such is rare accounting for 1% of all strokes.[1] Bilateral medial medullary syndrome is even more rare. Brainstem infarcts present with profound deficits because of the compact anatomical structures. Although ipsilateral cheiro-oral syndrome and crossed cheirooral syndrome (COS) have been reported in medullary infarct, bilateral sensory symptoms – cheiropedal syndrome (CPS) as the initial presentation in a medullary infarct has not been reported previously.[2] Sometimes, small sensory presentations can be a sentinel event before large medullary infarction. Here, we report the case having a history of restricted acral sensory syndrome (RASS) significantly before major deficits due to bilateral medial medullary infarction. CASE REPORT A 61-year-old morbidly obese (body mass index 39.2 kg/m2) patient, known diabetic, hypertensive and dyslipidaemia, chronic alcoholic and tobacco chewer (last intake 2 months back), developed sudden tingling in both upper limbs up to the elbow with mild imbalance in walking after waking up in morning 10 days back. However, he was able to do his daily activities and job without any difficulty. He consulted outside for the same and was advised antihypertensive in view of raised blood pressure. The symptoms remained static till the 11th day when patient presented to us after acute onset weakness of all four limbs, dysphagia, dysarthria and imbalance. Blood pressure at presentation was 140/90 mmHg. Examination revealed quadriparesis (right > left) with right UMN facial and right hypoglossal palsy, exaggerated deep-tendon reflexes, extensor right plantar and impaired joint position sense in the upper limbs up to wrist with preserved pain and temperature sensations. Rest of the neurological examination was unremarkable. The possibility of a vascular event in the form of stroke was considered given the sudden to acute presentation with a differential of brainstem encephalitis and the patient underwent neuroimaging. Magnetic resonance imaging of the brain revealed acute bilateral medial medullary infarction (heart sign) [Figures 1 and 2]. Computed tomography (CT) angiography of the neck to vertex showed athero-calcific disease in left vertebral and bilateral internal carotid artery along with possible partial thrombotic occlusion of proximal pulmonary arteries. CT pulmonary angiography suggested bilateral partial pulmonary artery thrombosis extending from the main trunk to segmental branches. Electrocardiogram showed sinus tachycardia and two-dimensional echo showed normal study. Complete haemogram, liver function and kidney function tests were within the normal limits. Lipid profile was in normal range (total cholesterol: 127.0 mg/dL, Serum Triglyceride: 84.0 mg/dL, high-density lipoprotein-cholesterol: 41.0 mg/dL and low-density lipoprotein-cholesterol: 79.0 mg/dL). Homocysteine levels were raised (21.92 mmol/L). D-dimer was elevated >5.50 mg/L (Normal <0.5 mg/L). Thrombophilia profile, including protein C, protein S, antithrombin III, prothrombin, factor V Leiden and MTHFR gene mutations, APLA antibodies and malignancy work up including prostate-specific antigen, Carcino-embryonic antigen and contrast-enhanced CT of the thorax with abdomen returned negative. He was started on low-molecular-weight heparin followed by the continuation of oral anticoagulants as Dabigatran 150 mg PO BD.Figure 1: Magnetic resonance imaging brain axial cuts show diffusion restriction (white arrow) in bilateral medial medulla (heart sign) in the diffusion weighted sequence (a) with low diffusion values (white arrow) in the corresponding region in the ADC maps (b) with hyperintense signal changes (white arrow) in FLAIR sequence (c) suggestive of acute infarctFigure 2: Heart sign – diffusion restriction in the bilateral medial medullary region resembling the shape of the heartOutcome/follow-up At 3 months’ follow-up, the patient was neurologically stable (modified Rankin scale of 0) The patient was able to walk independently with improved gait and dysarthria. DISCUSSION Medial medullary syndrome accounts for 1% of all the cerebral infarction.[1] MMS is known to classically present as a triad of contralateral hemiplegia, contralateral hemisensory loss involving fine touch, vibration and proprioception and ipsilateral paresis of the tongue. This is due to the arrangement of pyramidal tract, medial lemniscus and the hypoglossal nucleus anteroposteriorly in the medial medulla. The uncommon manifestations in a medial medullary syndrome include limb ataxia, nystagmus, diplopia, vertigo, dysarthria, dysphagia and UMN facial weakness.[3] Infarction in the medial medulla is due to the occlusion of the paramedian branches of the anterior spinal artery which is further a branch of the vertebral artery. Pure or predominant sensory stroke (PSS) is rare with the most commonly lesions in the thalamus.[4] PSS is also seen in the lesions of the brainstem with the lesions being lacunar infarcts or small haemorrhages. Brainstem lesions as the cause of PSS can be differentiated clinically by the frequent association of the other symptoms in brainstem strokes. Brainstem PSS is usually seen in lesions in the dorsolateral pons and is characterized by dominant lemniscal sensory modality or leg dominant pattern or RASS.[5] RASS refers to restriction of the sensory symptoms to the perioral region, palms and feet. RASS has been described in patterns of COS, Cheiro Oral Pedal syndrome and CPS.[6] The above patterns of sensory presentation have been attributed to the topographical representation of the parts in the sensory pathways in the brainstem. Pure or PSS-RASS with medullary stroke has been documented previously by Lin et al. where in 174 patients of COS, five patients had lesions in medulla and 4 of them progressed to Wallenberg syndrome.[2] In another study of 176 AIS patients with sensory symptoms, Akimoto et al. found only two patients with lesions in the medulla. Of the two, one with lesion in the medial medulla presented with CPS, the other with lesion in the lateral medulla presented with hypoaesthesia of the arm.[7] Kim studied 30 patients with RASS and the study showed that out of 30, 10 patients had RASS due to lesions in the brainstem. Two had lesions in the midbrain and 8 in the pons. None of them had lesions in the medulla.[6] Another case of 17 patients with PSS by Kim and Bae also showed majority of patients with lesions in the paramedian pons or dorsolateral pons and few patients in midbrain.[5] In a case series of medial medullary syndrome involving 86 patients, 12 had bilateral lesions and of the 12, only 1 had lesion in the middle part involving the medial lemniscus.[3] The nature of the clinical presentation in this patient was unknown. Another series of 11 patients with medial medullary syndrome by Toyoda et al. showed two patients with bilateral medullary lesions. Both of them had bilateral sensory symptoms in addition to other symptoms as well.[8] Our patient initially developed paraesthesias of both upper limbs with mild walking imbalance 10 days before the primary stroke. The initial sensory deficit may have resulted from a minor occlusion of the vertebral artery. Worsening after 10 days resulted from major re-infarction in the same area, the risk of which could have been reduced by early institution of antiplatelets at the symptom onset. Thus, acral sensory symptoms should lead to the suspicion of stroke in the brainstem area, with early neuroimaging helpful in detecting and preventing a major brainstem stroke. LEARNING POINTS Pure sensory stroke is a less common manifestation of medullary infarct RASS can foreshadow a major medullary infarction Recognition of RASS as brainstem stroke might give the treating physician an opportunity to avoid undue morbidity and mortality due to major infarct. 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