LESIONS

A Guide to Localisation in Neurology

Case 7. A weak hand on waking

Outcome

The initial review in the emergency department identified new-onset significant hand weakness, raising concern for a stroke. She had an urgent CT head which was normal. Blood tests were also normal.

She was then referred for a neurology opinion on suspicion of a radial nerve palsy given the selective weakness in certain muscles and sparing of others. The neurologist agreed after a detailed examination found features consistent with a radial palsy. The distribution of affected muscles suggested compression near the elbow.

Nerve conduction studies were considered but felt unnecessary – there was no real diagnostic doubt, so it would simply have confirmed what was evident and wouldn’t influence management. There was no suspicion of any of the other causes listed earlier such as fracture, so limb imaging was not performed.

She was managed conservatively, with physiotherapy input and an orthotic wrist splint to hold the wrist in a neutral position. This made it easier to hold objects – which is very difficult without the power to keep the wrist neutral (grip is challenging with a flexed wrist, even though the finger flexors are not radial-innervated). The patient took care to avoid further compression of the arm, ensuring she did not sleep in a chair, using padded arm rests if seated watching TV, and making sure to move the arm intermittently to prevent sustained positions.

Her weight loss was explored and attributed to limited oral intake in the recent months. She was given dietary support with supplements and her family provided support with meals. There was no suggestion of any sinister cause such as malignancy.

Her hand and wrist returned to normal in the next three months.

Radial nerve palsy due to compression at the elbow, triggered by sleeping in a chair.

• Acute-onset hand weakness is often due to a nerve palsy, but lesions in the motor cortex are also possible and can look similar - imaging is indicated if the distribution is not consistent with a nerve palsy
• The radial nerve has many branches, so localisation is possible depending on the clinical features
• We can distinguish radial and PIN palsies - the latter is motor only, and only partially affected wrist extension (with radial deviation during attempts)
• Wrist flexion limits non-radial nerve hand functions such as grip; a splint, which holds the wrist in a neutral position, enables these functions