Numbness

By Dr Roopa Jaiswal on the 30 August 2018

Causes of numbness range from the benign to severely life-threatening, says Dr Roopa Jaiswal.

Numbness can occur anywhere in the body, but is most commonly felt in the fingers, hands, feet, arms or legs (Photo: iStock.com/spukkato)

 

symptoms

• Sudden or rapid onset
• Confusion or loss of consciousness
• Slurred speech
• Change in vision
• Saddle anaesthesia
• Loss of bladder or bowel control
• Difficulty walking
• Numbness after a head, neck or back injury

Numbness is defined as loss of normal sensation that can occur anywhere in the body, but most commonly felt in the fingers, hands, feet, arms or legs. Patients may use 'numbness’ to describe loss of sensation, abnormal sensations, and weakness or paralysis.
It is often described by patients in conjunction with tingling or paraesthesia, very common symptoms encountered in primary care, and may be accompanied by pain, extremity weakness and non-sensory cranial nerve dysfunction. Causes of numbness range from the relatively benign to severely life-threatening.

Taking a history

There are many disorders causing numbness, so a systematic approach should be taken.
A key point to establish is the distribution of the numbness; which side of the body, and which aspect of the body part is involved (for example, the dorsal or ventral part of a limb).
It is paramount to note the rate of onset, duration of the numbness, whether it has been continuous or intermittent, and associated neurological symptoms, particularly red flag symptoms. Rate of onset in seconds or minutes suggests ischaemic or traumatic pathophysiology.
In the absence of symptoms suggestive of stroke requiring urgent transfer to secondary care, a review of systems will aid a differential diagnosis. Back or neck pain may be associated with a herniated disc or spinal cord compression.
Headaches could point towards a cerebral tumour, stroke or encephalopathy. Saddle numbness with or without bladder or bowel disturbance or sexual problems could indicate cauda equina syndrome.
B12 and thiamine deficiencies may become apparent from a nutrition evaluation and alcohol history.
Any history of cancer or risk factors for cancer should be elicited. Risk factors for stroke, diabetes and thyroid disease are all relevant, as are occupational and drug histories.

Neurological examination

Numbness in the presence of any red flag symptom warrants further investigations and possibly urgent admission, especially if a stroke is suspected.
A comprehensive neurological exam should look at both the cranial and peripheral nerves, especially noting the location and neurological territories of deficits in reflex, motor and sensory function.
Establishing if there is any weakness, asymmetry, drooping of the face, upper or lower motor neurone signs and saddle anaesthesia will guide as to the urgency.
In general, numbness of part of one limb suggests a peripheral nerve lesion while brain lesions would give rise to unilateral numbness of both limbs (this may include the trunk).
Bilateral numbness may be dermatomal, suggesting a spinal cord lesion. In the absence of a dermatomal distribution the aetiology may be a polyneuropathy, multiple mononeuropathy or a patchy spinal cord or brain disorder.

Possible causes

Neurological causes:

• Stroke/TIA
• Spinal nerve compression - metastatic malignancy, herniated disc
• Peripheral nerve compression - tumour, enlarged blood vessels, infection
• Seizures
• MS
• Nerve damage due to trauma

Vascular causes:

• Atherosclerosis
• Raynaud's sydrome

Endocrine causes:

• Diabetes
• Hypothyroidism

Vitamin deficiency(Vitamin deficiency):

• B12 deficiency(b12 vitamins).
• Thiamine deficiency(thiamine vitamin).

Nerve toxicity:

• Alcohol
• Lead
• Chemotherapy drugs

Electrolyte disturbances:

• Sodium, potassium and calcium

Hereditary degenerative disorders:

• Hereditary neuropathy with pressure palsies
• Charcot-Marie-Tooth disease

Further investigations

Further investigations may include blood tests such as FBC, U&Es, TFT, glucose, B12 and possibly a toxicology screen.
Patients may need to be referred to hospital. Imaging may include CT or MRI head and spine, and possibly ultrasound and X-ray.
Electromyography and lumbar puncture may be performed depending on the clinical indication.

• Dr Jaiswal is a GP in London