Background

The cortical “hand knob area” is located in the precentral gyrus in the shape of an inverted omega in the vast majority of cases, seldomly presented as a horizontal epsilon in the axial plane [1]. Infarction of this area can induce the focal weakness of contralateral hand or distal arm, occasionally combined with sensory deficits if the postcentral gyrus in the parietal lobe is also involved [2]. This rare type of acute stroke only accounts for less than 1% of all ischemic strokes, which is frequently at risk of being misdiagnosed as peripheral neuropathy. To our knowledge, there is no previous case presented with pain symptoms. We report a case whose primary symptom is wrist pain during sleep followed by focal fingers paresis missing the intravenous thrombolysis in emergency department.

Case presentation

A 70-year-old man awoke from sleep due to sudden pain of his right medial wrist at 21:30, meanwhile he felt difficulty in extending his right index and middle fingers. Two hours later he presented to the emergency department of our hospital since the symptoms persist. On admission, he also complained weakness of his right hand. He had past history of hypertension. Neurological examination showed paresis of extension of right index and middle fingers, and decreased gripping strength of right hand. There was no paraesthesia and the right finger-to-nose test could be done well with ring finger. The other neurological exam was unremarkable. The National Institutes of Health Stroke Scale (NIHSS) score was 0. After the assessment of stroke team, intravenous thrombolysis was not given based on the atypical symptoms and NIHSS score. Because of the acute onset of symptoms, besides the neurotrophic treatment, the antiplatelet and statin (atorvastatin) therapy were also administrated while we were scheduling the brain MRI (Siemens, Sonata, Siemens, Germany). The brain MRI showed multiple DWI hyperintense lesions (Fig. 1A), including partial left-hand knob area (black solid arrow) and its descending declining fibers (white solid arrow). CTA (Siemens, SOMATOM Definition FIASH, Siemens, Germany) showed a focal stenosis (> 75%) of proximal left internal carotid artery (white dashed arrow) with a lateral calcified plaque (black dashed arrow) (Fig. 1B). Dual antiplatelet therapy was scheduled for 90 days since the patient refused further endovascular treatment. The symptoms was almost relived at 90 days follow-up.

Fig. 1
figure 1

A Diffusion-weighted magnetic resonance imaging showing multiple acute infarctions involving partial left-hand knob area (black solid arrow) and its descending declining fibers (white solid arrow). B CT angiogram (CTA) showed a focal stenosis (>75%) of proximal left internal carotid artery (white dashed arrow) with a lateral calcified plaque (black dashed arrow)

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Conclusions

The rare infarction of cortical “hand knob area” only accounts for less than 1% of all ischemic strokes, which is frequently at risk of being misdiagnosed as peripheral neuropathy. The onset symptom of wrist pain during reported in our patient was different from previous studies and might increase the risk of misdiagnosis.

As for the etiology, although large arterial atherosclerosis (LAA) has been reported as one of the mainly etiologies since objective stenosis of carotid or intracranial arteries detected by angiography [3]. However, based on the brain MRI image of our patient, the arterial to arterial embolization caused by ruptured carotid plaque should be more exact etiology for our patient. Similarly, recent studies indicated that the hand knob infarction should more typically induced by embolism, including atheroembolism, cardioembolism as well as cancer-associated thromboembolism [4, 5].

Our case presented with a sudden onset of pain during sleeping, which might increase the risk of confusing the case with peripheral neuropathy since nocturnal pain of medial wrist was one of the most commonly reported symptoms in carpal tunnel syndrome. The coexisting infarction of inferior part of left posterior central gyrus might be the source of the pain symptom (white dashed arrow in Fig. 1A).

Therefore, we suggested that the hand knob infarction should be carefully inspected in patients with acute onset of focal hand paresis, even though there might be other uncommon symptoms such as wrist pain during sleep.