Dear doctor: nerve pains at night
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Dear doctor: nerve pains at night

From InterAction 92, spring 2016 

Our joint medical advisers, Prof Julia Newton and Dr Gregor Purdie, answer a reader's question about nerve pains at night.

For ten years now the nerve pains in my legs at night have been becoming progressively worse. I have muscle pain, to greatly varying degrees, all the ctime but this is nerve pain with occasional aching in the back of my knees and/or calf muscles.

The odd fact is that the pains can be in one or both legs, in any part of the leg, and only happens after I have been laying down in bed asleep for about 3-4 hours. It stops within a short time if I sit up in bed. It doesn’t happen during the day and seems to have no relevance as to whether or not I have done any walking. If I take a painkiller when I go to bed it has worn off by the time the pains start. Have you any suggestions and is this a common complaint in M.E.?

Prof Julia Newton says:

Thank you for your question regarding pain in your legs. It is extremely difficult to sometimes tell the difference between what is muscle pain, pain from the joints or pain related to nerves. Often people can feel pain in their legs which is actually related to arthritis or the trapping of nerves in their back. So, sometimes it can take a bit of delineating via the clinical history and/or investigations in order to determine the site of origin of the pain.

In terms of pain in the joints, pain in the back can be referred down the leg but often pain from the hip, pelvis or knees can cause problems of aching in the knees and calf muscles. If you are experiencing sensation of joints locking or giving way, or specific redness or swelling of the joints, then it is really important to see your GP to decide whether or not anything further needs to be done with regard to that.

With regards to pain in the muscles, this is sometimes there at rest but can frequently occur after exercise when it is described as post-exertional. Pain when you waken from sleep is quite unusual and makes me wonder whether you could have something like restless leg syndrome which is a condition that seems to be more common in people with fatigue and fatigue associated conditions. 

Restless leg syndrome is a wellrecognised primary sleep disorder and is often responsive to medications such as pramipexole and ropinirole. It is very easily diagnosed in a sleep clinic; sometimes it is just diagnosed on the basis of the clinical picture which is very characteristic and if there is some doubt about that then usually they will put activity monitors on people’s ankles and ask them to sleep with these and see whether there is any indication of excessive restlessness.

Things like gout or cramp, again, can cause problems with sleep which may manifest as aching of the calves, and again there are treatments available for both of these. If people have pain on exertion you do also wonder whether they have a problem with the blood vessels supplying their calves, whether perhaps these may be narrowed. So, feeling the pulses to see whether there is vascular disease is also very important.

Research into muscles

Recently my team in Newcastle have been doing some research work in patients with fatigue, particularly M.E./CFS, where we have been exercising muscles in the MRI scanner and looking at how acid accumulates. We were able to show, using MR spectroscopy, that people with M.E./CFS accumulate about 20 times more acid in their muscles in response to exercise, compared to matched controls. 

Some of the volunteers who very kindly participated in the MRI studies donated muscle cells and we have been performing experiments in the laboratory to look at how these muscle cells use energy when they exercise. We have recently shown that there are abnormalities in biochemistry as the muscle cells exercise in those who have M.E./CFS, with particular impairment of a molecule called AMP Kinase.

We are now doing further work (some of it supported by Action for M.E.) where we look in more detail at AMP kinase and whether we can influence it in the laboratory. The hope ultimately would be that we would be able to develop or repurpose medications that might allow people to have muscle cells that utilise energy more efficiently.

Dr Gregor Purdie says:

As Julia has explained, it can take a lot of work to come to a diagnosis when a patient comes into surgery complaining of nerve pains in their legs. Please bear with your GP as it can take at least two appointments to come towards a diagnosis depending on the complexity of the symptoms and awaiting blood test results.

It is central to the consultation that your GP gets the complete story of your symptoms. The first thing that I would ask would be for the patient to describe their pains in detail.

  • What is the character of the pain? For example it could be sharp or stabbing or throbbing.
  • What is the intensity of the pain? How would you rate it on a scale of 1 to 10? Does it come and go? What makes it worse? What have you noticed that can ease it off?
  • The distribution of the pain is also very important. Where on your body does the pain lie (ie. the seat of the pain)? Does it move anywhere else?

Examinations and tests

A physical examination is also very important. Once the area afflicted by the pain has been identified, the GP will also examine joints in the affected area. Is there local heat, local redness (signs of local inflammation such as in inflammatory joint disease as in forms of inflammatory arthritis)? Is there sensitivity in the skin, which you can get with some nerve pains? Are the muscles tense? How mobile are the joints compared to normal? 

We still use tendon hammers to test reflexes. This is valuable in assessing nerve pains originating in the back such as sciatica. If the nerve pain could be related to your back, you will be asked to lie flat on your back and your legs will be lifted straight, one at a time to see if there is any restriction of movement caused by increasing pain from lifting the leg. This again helps to assess whether the pain could be originating from your back.

There are simple blood tests that can aid diagnosis. A C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are tests of inflammation in the body and are raised in conditions such as rheumatoid arthritis. A creatine kinase (CK) is a test of muscle pain and muscle inflammation.

If there are neurological signs found on examination that require further investigation then referral to a neurologist would be appropriate.

I always keep in my mind that it is important to consider all causes of the pain and not fall into the trap of “it’s just your M.E.”

Get in touch with your queries for our joint medical advisers, Prof Julia Newton and Dr Gregor Purdie, about medical matters. We regret that they cannot respond to individual enquiries.