Stroke Note Received: May 23, 2013 Accepted: August 6, 2013 Published online: November 28, 2013 Cerebrovasc Dis 2013;36:462–463 DOI: 10.1159/000354861 Mono-Limb Ataxia Caused by Motor Cortical Infarction: Case Report and Review of the Literature Department of Neurology, University of Ulsan, Asan Medical Center, Seoul, Korea Although small cortical infarctions in the primary motor cortex usually present with distal limb weakness [1], ataxia has been reported to be caused by such lesions [2–4]. However, due to the rarity of the cases, the lesion location and the presumed pathogenic mechanism have not been sufficiently discussed. We herewith describe a patient with isolated mono-limb ataxia caused by a stroke occurring at the motor cortex adjacent to the hand knob area, and review the previous literature. Case Report A 75-year-old hypertensive man with atrial fibrillation suddenly felt a sensation of clumsiness in the right hand while using chopsticks. His past history showed that he had developed aphasia and right limb weakness due to a left middle cerebral artery territory infarction 7 years before. After thrombolysis therapy, his neurological deficits completely resolved, and there was no functional impairment afterwards. Neurological examination on admission showed normal articulation, muscle power, reflexes, and sensory perceptions. The finger-to-nose test showed a marked intention tremor and pastpointing in the right arm. Dysdiadochokinesia was also observed. However, no ataxia was observed in the lower extremities evaluated by the heel-to-shin test, and the tandem gait was normal. Diffusion-weighted MRI (DWI) performed 6 h after the onset showed a focal ischemic lesion located slightly medial to the precentral hand knob area (fig. 1). There was an old infarction in the left insular cortex, but no acute or chronic structural lesions were observed on the cerebellum or brainstem. Discussion The patient presented with mono-limb ataxia associated with cortical infarction. Although he had a previous infarction, the related neurological symptoms completely resolved afterwards, and the patient’s current ataxia was caused by the new, cortical infarction. Through a literature review, we could identify 6 additional © 2013 S. Karger AG, Basel 1015–9770/13/0366–0462$38.00/0 E-Mail karger@karger.com www.karger.com/ced References 1 Back T, Mrowka M: Infarction of the ‘hand knob’ area. Neurology 2001; 57:1143. 2 Noda K, Miwa H, Miyashita N, Tanaka S, Mizuno Y: Monoataxia of upper extremity in motor cortical infarction. Neurology 2001; 56: 1418– 1419. 3 Ota S, Tsuchiya K: Cerebral small infarcts of the precentral and postcentral gyri presenting with unilateral monoataxia: a report of two cases (in Japanese). No To Shinkei 2005;57:1083–1087. 4 Sellbach AN, Wong AA, Boyle RS: Ataxia due to isolated infarction of the precentral knob. Mov Disord 2008;23:1789–1791. 5 Brodal P: The corticopontine projection in the rhesus monkey: origin and principles of organization. Brain 1978;101:251–283. 6 Prats-Galino A, Soria G, de Notaris M, Puig J, Pedraza S: Functional anatomy of subcortical circuits issuing from or integrating at the human brainstem. Clin Neurophysiol 2012;123:4–12. 7 Lin DD, Kleinman JT, Wityk RJ, Gottesman RF, Hillis AE, Lee AW, Barker PB: Crossed cerebellar diaschisis in acute stroke detected by dynamic susceptibility contrast MR perfusion imaging. AJNR Am J Neuroradiol 2009;30:710–715. 8 Catani M, Dell’acqua F, Vergani F, Malik F, Hodge H, Roy P, Valabregue R, Thiebaut de Schotten M: Short frontal lobe connections of the human brain. Cortex 2012;48:273–291. Jong S. Kim, MD, PhD Asan Medical Center University of Ulsan College of Medicine Asanbyeongwon-gil 86, Songpa-gu, Seoul 138-736 (Korea) E-Mail jongskim @ amc.seoul.kr Downloaded from http://karger.com/ced/article-pdf/36/5-6/462/2351697/000354861.pdf by guest on 12 April 2024 Bum Joon Kim, JuKyung Lee, Jong S. Kim patients who developed limb ataxia due to infarcts occurring at the motor cortex. Including ours, all patents showed a lesion located just medial to the hand knob area (fig. 1). In two patients (No. 6 and 7) who had hand clumsiness as well, the lesions were slightly extended to the hand knob area. The cortico-ponto-cerebellar tract originates from the central regions of the cerebral cortex [5] and runs antero-medially adjacent to the corticospinal tract [6]. The characteristic lesion location, i.e. just medial to the hand knob area, in our patient and those described in the literature suggests that this tract may be selectively interrupted by the lesion, resulting in prominent ataxia. The symptom may also be explained by impaired blood flow and neuronal metabolism in the contralateral cerebellum due to supratentorial infarcts (crossed cerebellar diaschisis) [7]. Alternatively, the lesions are located in the transition zone between the primary motor and sensory cortex where short frontoparietal U shape tracts are located [8]. Disconnection of these fibers may interrupt the sensory input travelling to the motor output area, thereby producing limb incoordination. Due to the small size of the lesion, these affected fibers cannot be assessed by tractography, and the hypothesis remains to be proven. Nevertheless, our report and review of the literature provide solid evidence that mono-limb ataxia can be caused by a cortical lesion strategically located in the motor cortex. Case 1 Hypertension Atrial fibrillation 3 [2] 69/M 67/M Diabetes Hypertension Clinical description Schematic lesion location Medial Oscillation of the left arm and shoulder during the finger-to-nose test Normal finger movements Rt. Medial Severe oscillation of the left arm and shoulder during the finger-to-nose test No loss of dexterity in the fingers and hand Rt. Medial 4 [3] 76/M Hypertension Cerebellar ataxia in the left upper extremity Rt. 5 [3] 90/F Hypertension Medial Cerebellar ataxia in the left upper extremity Rt. 6 [4] 7 [4] 43/M 85/M Diabetes Smoking Hypertension Hyperlipidemia Medial Bilateral past pointing in the figner-tonose test Bilateral hand dysdiadochokinesia Rt. Intention tremor on the figner-to-nose test in the the right arm Medial Right hand dysdiadochokinesia Lt. Lt. Fig. 1. Demographics, risk factors, neurological deficits, and DWI findings of our patient (case No. 1) and 6 additional patients (case No. 2–7) from the literature review. The arrows in case 1 indicate the ischemic lesion adjacent to the hand knob area. In cases 2–7, the dark line is a schematic illustration representing the outline of the precentral motor cortex including the hand knob area. The black circles are the relevant infarcts. The gray circle in patient No. 4 represents an old infarct. Ages are presented in years. ref. = Reference; Rt. = right; Lt. = left. Ataxia Caused by Cortical Infarction Cerebrovasc Dis 2013;36:462–463 DOI: 10.1159/000354861 463 Downloaded from http://karger.com/ced/article-pdf/36/5-6/462/2351697/000354861.pdf by guest on 12 April 2024 Risk factors Hypertension 2 [2] Intention tremor and past-pointing on finger-to-nose test in the right arm Dysdiadochokinesia in the right arm Lesion location: Patient No. Age/sex and ref. 75/M Clinical descriptions: Risk factors: