In short. Mapping the area, testing light touch, pinprick and temperature, and what nerve studies add and cannot add when sensation is altered after an operation.
Key points
- It can say where feeling is reduced and how severe that is.
- It cannot say whether the nerve is divided, bruised or compressed, and it cannot predict how much feeling will return.
- Those are judgements made from the direction of change over months, from what was found at the operation, and from the pattern of the loss.
An assessment of altered feeling after an operation begins with a conversation and a map, not a machine. The examination establishes where feeling is reduced, how much it is reduced, and whether anything besides feeling is affected. Nerve studies have a real but narrow place, and knowing what they can and cannot show prevents a common disappointment.
Mapping the area
The first step is to define the territory. The clinician marks the border of the numb area and records its shape, then compares it against what the operation performed would be expected to produce. A patch that follows the incision is ordinary. A patch that extends well beyond it, follows the territory of a named nerve, or has appeared where the operation did not reach tells a different story and directs the examination.
Light touch, pinprick and temperature
Feeling is tested by comparing the two sides. Light touch is tested with a wisp of cotton or a fingertip, pinprick with a disposable pin, temperature with something cool, and vibration with a tuning fork. Deep pressure is tested separately, because it travels on different fibres from light touch. Each test answers a slightly different question, which is why a proper assessment uses several rather than one.
What the examination cannot do
It can say where feeling is reduced and how severe that is. It cannot say whether the nerve is divided, bruised or compressed, and it cannot predict how much feeling will return. Those are judgements made from the direction of change over months, from what was found at the operation, and from the pattern of the loss.
What nerve studies add
Nerve conduction studies and electromyography measure how well a nerve carries a signal and whether muscle is still supplied. They are most useful where movement is affected, where a nerve may be compressed away from the operation site, or where the clinical picture does not fit the expected anatomy. They are much less useful for the fine sensory branches in skin, which are too small to measure reliably. A normal study does not mean feeling is normal.
What else is looked for
The assessment also looks for the things that can press on or tether a nerve: a scar that has formed across it, a collection of fluid or blood, swelling that has not settled, and infection in the wound. An ultrasound scan may be used to look for a collection or to follow a nerve along its course. The examination always finishes by testing movement, because a motor finding changes the urgency of everything else.
Seek emergency care now if
- There is new weakness, or a limb or a face that will not move as it should.
- A limb is cold, pale or blue, or there is severe pain with the numbness.
- There is loss of bladder or bowel control, or numbness around the groin.
The point of all of it is a direction of travel and a decision, rather than a test result on its own.
Frequently asked questions
Why does the clinician test movement first?
Because a motor finding changes the urgency and the timetable. Feeling and movement travel on different fibres, and if a muscle group is not working as it should, the problem is no longer confined to the skin and the interval for repair becomes much shorter. That single answer redirects the whole assessment.
What does a normal nerve study mean?
It does not mean feeling is normal. Nerve conduction studies and electromyography measure how well a nerve carries a signal and whether muscle is still supplied, which is most useful where movement is affected. The fine sensory branches in skin are too small to measure reliably, so a normal study can coexist with a clearly numb patch.
Can an examination tell whether the nerve is cut or bruised?
Not on its own. An examination can say where feeling is reduced, how severe it is, and whether movement is affected. Whether a nerve is divided, bruised or compressed is judged from what was found at the time of the operation, from the pattern of the loss, and from how the area changes over months.
Risks & Limitations
- Numbness around an incision is expected after almost every operation, because small sensory nerves in the skin are divided or stretched.
- Recovery of feeling is measured in months and is uneven; some patches wake up early and others lag, and the direction of travel matters more than the severity.
- Some numbness never fully recovers, particularly after a large incision, a second operation through the same area, or a branch that had to be divided.
- Fine touch is the last thing to return and the last thing to be trusted, while deep pressure and pain are often preserved when light touch is not.
- Numb skin cannot warn you, so heat, sustained pressure and sharp edges injure it without pain; a daily look at the area is what replaces the missing warning.
- Numbness is a feeling problem and weakness is a movement problem. Weakness, a cold pale limb, saddle numbness and loss that is spreading need emergency assessment rather than a routine review.
When to Seek Care
- Weakness with the numbness: a limb that will not move, a foot that drags, a face that droops, or an eye that will not close — seek emergency care now.
- A limb that is cold, pale or blue, or severe pain with the numbness — seek emergency care now.
- Loss of bladder or bowel control, or numbness around the groin and inner thighs — seek emergency care now.
- Numbness that is spreading rather than settling, or that arrives with new swelling, heat, redness or a fever — seek care the same day.
- Burning or electric-shock pain that is worsening rather than easing — have it assessed within days.
References & Further Reading
- World Health Organization (WHO) — patient safety and surgical care guidance
- National Institute for Health and Care Excellence (NICE, UK) — guidance on nerve injury and rehabilitation
- American Society of Plastic Surgeons (ASPS) — procedure and safety guidance
- National Health Service (NHS, UK) — information on nerve pain and altered sensation
- Chinese Medical Association Plastic Surgery Branch — clinical guidance
This page is patient education, not medical advice, and it does not cite individual studies. Discuss your own case with a qualified clinician. To arrange an assessment at Chongqing West District Hospital, see Contact & Consultation.