Clonus after lumbar fusion

I had a two level fusion with plates and screws and BMP done on 6/30/09.  I had L3-L5 fused, and then some bone spurs were removed at L5-S1. After surgery my leg pain was pretty much resolved, although my back pain was worse than ever.  Unfortunately, after about 5 months I started experiencing numbness, burning and tingling in my right leg.  I returned to work on 1/4/10 (sedentary job) and by day three, I developed severe numbness, tingling, prickleys, burning, in both legs.  My Neurontin was increased to 1800mg, and I underwent a caudal injection about 2 weeks ago.  The injection has seemed to help some, but I am still experiencing symptoms, especially in my right foot, where it feels hot and numb, tingling, etc.  My back remains horrible.  Unfortunately despite therapy and medications, it is still unbearable.  I went to PT this past Friday, and he indicated that my legs were VERY ratchety, I am assuming he meant clonus, because they were kind of shaking up and down.  He said he sees this quite frequently in fusion patients, but not to this extent. He was going to call my pain doctor to see if perhaps this could be caused by the medications I am on. I am taking oxycontin, norco, baclofen, valium, neurontin and cymbalta.   I saw my surgeon in December and he said it was too early to tell, but if I was still experiencing the leg symptoms he would order at CT scan. My pain doctor seems to think there may be more going on. Should I be concerned about this latest development with the ratchety muscles, and the worsening of the leg complaints, or am I just jumping the gun because it does take a while for a fusion to heal? Is it possible that the medications I am on is causing the ratchety/clonus muscles?  

[Neuro Forum]

Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.

Without the ability to examine you and obtain a history, I can not tell you what the exact cause of your symptoms is. However I will try to provide you with some useful information.

I am not sure what your therapist meant by rachety, so I can not comment on whether or not there is clonus on your examination. In general, clonus and certain other physical examination findings are suggestive of a problem in the spinal cord itself; the spinal cord ends above the L3 level, so involvement of the spinal cord would be unlikely based on the pathology you describe above, unless you have lesions higher up in the spinal cord. If there is a diffuse problem with nerve roots (the nerves after they exit the spinal cord in an area called the cauda quina) such as infection, then both legs would be affected. Otherwise, if it is just nerves on one side of the spine, this would not explain burning in both legs. Burning in both legs could be due to a problem unrelated to the spine issues: a neuropathy.

Neuropathy is a generic term for a disorder of the peripheral nerves. The symptoms of neuropathy including burning, pain, tingling, numbness in the hands and feet, and when severe, motor weakness. There are several causes to neuropathy including most commonly diabetes, and sometimes only glucose intolerances, or abnormal rises in blood sugar after a glucose load can be the only indication (this is called a oral glucose tolerance test. Other causes include but are not limited to hereditary/genetic causes, autoimmune problems, and demyelinating diseases (such as CIDP). Vitamin B12 and B6 deficiency, as well as excess vitamin B6, can also cause neuropathy. Some toxins, such as lead, arsenic, and thalium can cause large fiber sensory neuropathy. Other causes include abnormalities of protein metabolism.

There are 2 types of nerves in our body, large and small. The small nerve endings supply the skin and sweat glands. There are two types of sensory neuropathy: small fiber and large fiber (depending on the size of the nerves affected). With small fiber neuropathies, symptoms including burning or buzzing or other vague symptoms starting in the feet and hands then in some cases spreading to other parts of the body. The diagnosis of large fiber neuropathy is made by findings on a test called EMG/NCS which assess how well the nerve conduct electricity and how well muscles respond. With small fiber neuropathies, symptoms including burning or buzzing or other vague symptoms starting in the feet and hands then in some cases spreading to other parts of the body. The EMG/nerve conduction studies (NCS) (tests done to check for neuropathy) will not show an abnormality, and a definitive diagnosis can only be made with a skin biopsy so that the number of nerve endings can literally be counted. There are other tests of the function of small nerves that can be ordered, such as QSART testing which looks at how much sweat the skin makes, since sweating is in a sense of function of these small nerves.

If your spine surgeon does not feel your spine surgery/spine issues explain your leg symptoms, then evaluation by a neurologist is recommended.

Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.