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LETTER TO EDITOR
Year : 2020  |  Volume : 68  |  Issue : 6  |  Page : 1493-1494

Acute Stroke Presenting as Isolated Orthostatic Negative Myoclonus


1 Department of Neurology, Narayana Multispeciality Hospital, Mysore, Karnataka, India
2 Department of Radiology, Narayana Multispeciality Hospital, Mysore, Karnataka, India
3 Department of Medicine, Narayana Multispeciality Hospital, Mysore, Karnataka, India

Date of Web Publication19-Dec-2020

Correspondence Address:
Dr. Vikram V Holla
Department of Neurologist, Narayana Multispeciality Hospital, Mysore, Karnataka - 570019
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.304092

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How to cite this article:
Holla VV, Pene SS, Kumar N. Acute Stroke Presenting as Isolated Orthostatic Negative Myoclonus. Neurol India 2020;68:1493-4

How to cite this URL:
Holla VV, Pene SS, Kumar N. Acute Stroke Presenting as Isolated Orthostatic Negative Myoclonus. Neurol India [serial online] 2020 [cited 2021 Jan 20];68:1493-4. Available from: https://www.neurologyindia.com/text.asp?2020/68/6/1493/304092




Sir,

Diagnosis of stroke when suspected can be easily made these days with a help of magnetic resonance imaging (MRI). Problem arises when MRI is contraindicated. More so when the presentation is also atypical. We came across one such case where atypical presentation and contraindication to MRI made the diagnosis challenging.

A 68-year-old elderly diabetic gentleman with mechanical aortic valve in situ presented with acute onset walking difficulty of one day with tendency to fall while walking. Patient reported he feels sudden giveaway predominantly in left knee on walking. No symptoms when in supine position. Patient had significant orthostatic hypotension (OH) but without dizziness. Gait was cautious with tendency to fall while walking due to knee buckling. Limb power and plantar reflex were normal with no rest or postural tremor/myoclonus. Computed tomography (CT) of the brain at admission to look for stroke was unremarkable. MRI was contraindicated due to mechanical valve. Postural symptom was attributed to OH and managed with stockings and fludrocortisone. Symptoms persisted despite improvement in OH. In view of postural symptoms, a phenomenon like limb-shaking transient ischemic attack was suspected and CT angiography brain was done to look for critical stenosis. Angiography was normal, but there was right anterior medial frontal hypodensity suggesting acute infarct [Figure 1]. Diagnosis of orthostatic negative myoclonus secondary to stroke was made. Clonazepam was added and improved significantly over next 1 week.
Figure 1: Repeat CT brain showing right anterior medial frontal region acute infarct

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Gait abnormality due to sudden knee buckling is commonly seen due to quadriceps weakness caused by various neuromuscular disorders with other causes being cataplexy, chorea, dystonia, orthostatic myoclonus, and functional gait disorders.[1] Orthostatic negative myoclonus as the name suggest is a negative myoclonus that occurs in upright position. It can be associated with positive myoclonus and other neurodeficits or can occur isolated.[2] It causes include postanoxic encephalopathy, frontal vascular lesions, atypical  Parkinsonism More Details, Alzheimer disease, normal pressure hydrocephalus, or can be idiopathic.[1],[3] Gait impairment in our patient was due to sudden knee buckling by isolated orthostatic negative myoclonus. There was neither clinical evidence of positive myoclonus nor any other neurodeficits. Although acute unilateral presentation in at risk individual suggested a vascular aetiology like stroke, isolated orthostatic presentation without other upper motor neuron signs, initial normal CT brain, and contraindication for MRI posed diagnostic difficulty. Presence of significant OH also acted as a confounder as OH can cause gait disturbance without frank dizziness in some cases. Presence of acute infarct in repeat CT brain helped to clinch the diagnosis and resolution of symptom with proper medication.

To conclude, frontal lobe strokes can have myriads of atypical nonparetic manifestations of which isolated orthostatic negative myoclonus is one. High index of suspicion is required to diagnose such cases. Also, when there is a suspicion of stroke and MRI is contraindicated, a repeat CT scan is warranted if first scan is normal as small infarcts may not be picked up by CT in first 24 to 48 hours.

Financial support and sponsorship

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  References Top

1.
Nonnekes J, Goselink RJM, Růžička E, Fasano A, Nutt JG, Bloem BR. Neurological disorders of gait, balance and posture: A sign-based approach. Nat Rev Neurol 2018;14:183-9.  Back to cited text no. 1
    
2.
Hassan A, van Gerpen JA. Orthostatic tremor and orthostatic myoclonus: Weight-bearing hyperkinetic disorders: A systematic review, new insights, and unresolved questions. Tremor Other Hyperkinet Mov (N Y) 2016;6:417.  Back to cited text no. 2
    
3.
Erro R, Bhatia KP, Cordivari C. Shaking on standing: A critical review. Mov Disord Clin Pract 2014;1:173-9.  Back to cited text no. 3
    


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