Upper extremity weakness due to cerebral metastasis involvin
Pseudoperipteral hand palsy is most frequently caused by a small lesion in the contralateral motor cortex of the brain. The ‘hand knob’ area refers to a circumscribed region in the precentral gyrus of the posterior frontal lobe, the lesion of which leads to isolated weakness of the upper extremity mimicking peripheral nerve damage. The etiology of this rare syndrome is almost exclusively related to an embolic infarction.

The present case report published in the journal BMC Cancer describes the case of a 70-year-old male patient with isolated left-sided upper extremity weakness and clumsiness without sensory disturbance suggesting a lesion of the radial nerve. Nerve conduction studies had normal results excluding peripheral nerve damage.

Neuroimaging (cranial CT and MRI) detected 3 space occupying lesions, one of them in the right precentral gyrus. An irregularly shaped tumor was found by CT in the left lung with multiple associated lymph node conglomerates. The metastasis from this mucinous tubular adenocarcinoma with solid anaplastic parts to the ‘hand knob’ area was responsible for the first clinical sign related to the pulmonary malignancy.

Key takeaway:-
- Pseudoperipheral palsy of the upper extremity is not necessarily the consequence of an embolic stroke.

- If nerve conduction studies have normal results, neuroimaging – preferably MRI – should be performed, as lesion in the hand-knob area of the precentral gyrus can also be caused by a malignancy.

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