Paraesthesia is an abnormal sensation of the skin, sometimes without any apparent cause. The sensation is often described with one or more of the following words or phrases: tingling, pins and needles, prickling, burning, chilling, and numbness. Some people will experience this as a feeling in the whole limb or perhaps only the lower leg or foot. Some people described this as feeling as if the leg or foot “has fallen asleep”, or as if there are “bugs underneath the skin”.
Paraesthesia may be a transient (temporary) or chronic issue (ongoing for more than 6 weeks). Transient paraesthesia may result from an acute compression (squashing) of a nerve, such as when “hitting your funny bone”, i.e. compressing the ulnar nerve, or the tingling and numbness experienced in the foot or feet of someone with sciatic nerve impingement. It may also arise from sustained pressure on the tissues surrounding a nerve or group of nerves, such as when sitting with your legs crossed for too long, causing the foot or leg to go numb followed by uncomfortable sensations when the blood flow returns. A third cause of transitory paraesthesia is a temporary reduction in blood supply to the nerves without sustained pressure, such as what happens in people who experience Raynaud’s Syndrome. Other causes of temporary paraesthesia include panic attacks and hyperventilation.
Chronic paraesthesia may have dozens of possible underlying causes, but usually indicates improper functioning of the nerves and/or poor arterial circulation. A common cause of paraesthesia in the lower limb is Peripheral Arterial Disease (PAD). PAD arises from atherosclerotic changes to the arteries in the lower limb, leading to thickening, hardening, and narrowing of the intra-luminal space through which blood is meant to flow. If the nerves cannot get the blood supply they require, they will be unable to function property, leading to paraesthesia. Other internal causes of chronic paraesthesia include:
- Diabetes-induced peripheral neuropathy (nerve damage) and/or ischaemia (poor blood supply).
- Underactive thyroid and underactive parathyroid.
- Chronic foot deformity and lower back or spinal issues leading to chronic neuropathy.
- Chronic infections such as Lyme’s Disease or Varicella Zoster (“Shingles”).
- Chemotherapy-induced peripheral neuropathy.
- Withdrawal from Benzodiazepines.
Treatment for paraesthesia of the leg and foot involves treating the underlying causes or condition with the appropriate lifestyle changes, physical treatments and medication. Podiatrists are able to assess patients for peripheral arterial disease using hands on techniques, an ultrasound doppler, and a procedure called an “Ankle Brachial Pressure Index” (ABPI), along with appropriate questioning regarding symptoms. If these tests are positive for PAD, then the podiatrist will refer you to your GP or a vascular consultant for further investigation and treatment. Podiatrists can also determine if a person has neuropathic changes which may be leading to paraesthesia. This is done by using a collection of non-invasive tools to test the activity or lack of activity in different sensory and motor nerve fibres of the foot and lower leg. If neuropathy is suspected, then referrals to the appropriate professionals will be provided. If you are experiencing paraesthesia in the foot or lower leg, arising from chronic compression or entrapment of a nerve in the back, leg or foot, then a podiatrist may be able to help with exercises, medical-grade insoles, acupuncture, and with appropriate referrals (MRI scans on lower back, osteopathy or physiotherapy, orthopaedic surgery, etc).