How can I test whether it follows a neck/nerve pattern (dermatome)?

The short version: a pinched nerve follows a dermatome, a stroke does not, and the fastest test is the pattern of onset plus whether the face or speech is involved.

A dermatome is the skin area served by one spinal nerve root. A pinched nerve at C6 or C7 produces tingling that follows that root's territory, but the overlap is real: one study of surgically confirmed C6 and C7 radiculopathies found the sensory loss zones overlapped so much that sensory exam alone could not reliably tell them apart [1]. So a dermatome test is useful for ruling out stroke, not for pinpointing the exact level.

The practical test has three parts. First, timing: stroke is sudden, seconds to minutes; a pinched nerve comes on gradually or after a specific neck movement. Second, spread: stroke affects whole systems, so check the face for droop, speech for slurring, and both arm and leg on the same side. Third, the nerve path: a pinched nerve stays in one arm, follows a stripe from shoulder to thumb (C6) or middle finger (C7), and does not touch the face or speech. One study of stroke patients found tongue deviation in 29%, always toward the weak side, and nearly all had speech trouble [1]. That combination, sudden onset plus face or speech involvement, is your stroke red flag.

My call: if onset was sudden or the face or speech is involved, treat it as a stroke and get emergency care now. If it came on gradually, follows a single arm stripe, and spares the face and speech, a pinched nerve is far more likely. Confidence: moderate. The dermatome overlap data is solid, but no study directly compares stroke versus pinched nerve head-to-head, so the distinction rests on pattern recognition, not a single test.