Saturday Night Palsy and Radial Nerve Compression

Falling into a heavy sleep with your arm pinned under your head or draped over a chair can compress a nerve in a very specific spot, and wake you up with a wrist that won't lift.
Where the Name Comes From
'Saturday night palsy' is an old but still-used clinical term for a radial nerve palsy, a dramatic example of radial nerve compression. that develops after the nerve is compressed against the humerus, the upper arm bone, for a prolonged period, usually during unusually deep or heavy sleep. The name comes from its classic association with falling asleep in an awkward position after a big night out, where alcohol's sedating effect meant the person didn't wake or shift position despite sustained pressure on the arm.
The same injury happens well outside that specific scenario, anyone who falls into an unusually deep sleep, whether from exhaustion, medication, or simply an odd position on a couch or armrest, can develop the same nerve compression. It's really a mechanism, not a lifestyle diagnosis.
Where the Nerve Is Actually Compressed
The radial nerve winds around the back of the humerus in a groove partway down the upper arm, the spiral groove, where it sits directly against bone with very little soft tissue cushioning it. In this position, the nerve is particularly vulnerable to sustained external pressure, such as an arm draped over the hard edge of a chair, resting under a partner's head, or hanging off the side of a couch for an extended period.
This is a different compression site to radial tunnel syndrome,, which affects a branch of the radial nerve much further down, near the elbow. The two conditions share a nerve but not a location, and they produce quite different symptom patterns as a result.
How It Presents
The hallmark sign is wrist drop, an inability to extend the wrist and fingers, so the hand hangs limply when the arm is held out. This happens because the radial nerve, at this level, supplies the muscles responsible for extending the wrist and fingers, and compression disrupts that function fairly abruptly rather than building gradually.
Numbness or altered sensation over the back of the hand and forearm often accompanies the weakness, though grip strength itself can be relatively preserved initially, since the muscles that close the hand are supplied by different nerves. People typically notice it immediately on waking, rather than it developing gradually through the day.
What Determines Recovery
Most cases of Saturday night palsy are what's known as a neurapraxia, a temporary conduction block in the nerve caused by compression, without the nerve fibres themselves being cut or structurally damaged. This type of injury generally carries a good outlook for recovery, often over a period of weeks, though the exact timeframe depends on how long and how significant the compression was.
More prolonged or significant compression can cause a greater degree of nerve fibre damage, which may extend the recovery timeline considerably. This is part of why an early assessment matters, distinguishing a straightforward neurapraxia from a more significant injury changes both the expected timeline and the rehabilitation approach.
What Helps While the Nerve Recovers
A wrist splint is often used in the interim to hold the hand in a functional position and help prevent overstretching of the weakened muscles and tendons while nerve function returns. Alongside that, gentle nerve mobilisation and monitoring of muscle and nerve function over time help track whether recovery is progressing as expected.
If wrist drop and numbness haven't shown any improvement after a few weeks, or if the weakness is severe from the outset, further assessment, including nerve conduction studies in some cases, is worth pursuing to rule out a more significant nerve injury and to help guide the right rehabilitation plan going forward.
Related Reading
← Back to the full Nerve Pain guideFor educational purposes only. Does not supersede advice from your GP or specialist.
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