Learning Objectives
- In PN, symptoms should be the same on both sides, longest nerves affected first
- Many cases of PN are associated with hyperglycemia
- Some causes of PN are never found
History
IP, a 67 year old hotel manager, visits the office with a symptom of numbness affecting both feet. The symptoms are the same on both sides. The area of the feet that is affected is the dorsal and plantar side of the feet, below the ankles. It is not clearly worse with rest or activity, although his feet are bothered by touching the bed sheets at night. He says they feel like they are very warm or on fire. The symptoms occur every day, and they have been occurring for about 10 months. He has no history of back pain, injury, or difficulty with urine or bowel function. He has not tried any treatments for this, but he would like to try one. He is especially curious about the cause of the symptoms.
He has a history of mild diabetes mellitus and alcoholism. He takes the medicine glucophage daily, and he has no allergies to medications.
His father had diabetes mellitus and passed away of a stroke at age 75. His mother has essential tremor.
He does not smoke or drink now, but over 20 years ago he smoked and drank daily. He has been sober for 22 years.
Review of ten systems reveals these pertinent negatives: he has had no fevers, no rashes, joint pains or myalgia. Bowel and bladder function are normal. The remainder of his ROS is negative.
Examination
He has a pulse of 77 and a blood pressure of 130/81. He is a pleasant, mildly obese fellow who appears appropriate for his age. His heart sounds are normal and carotid artery auscultation is normal. His pupillary exam is normal. He speaks easily, and he is fluent and oriented. His ocular movements are intact and conjugate. His upper and lower facial movement is symmetric. Facial sensation to touch and pin is normal. Tongue is midline and sternocleidomastoid movement is normal. His arm strength and tone are normal. There appears to be atrophy of the tibialis anterior and the extensor digitorum brevis on both sides, and his toes are flexed (hammer toes). These atrophic muscles are mildly weak. His biceps reflexes are normal, patellar reflexes are reduced, and Achilles reflexes are absent. Toes do not appear to respond to Babinski testing. His hands have normal sensation. There is a loss of vibratory sensation in the feet, below the ankles. He has lost sensation to proprioception in the great toes, and to pin prick, in the lower legs extending to the mid calf. Heel knee shin and finger nose finger movements are normal. He is able to walk on his toes and his heels. Romberg testing is negative (normal).
This person has diminished sensation in a region similar to that covered by a stocking, on both sides, with diminished reflexes, and atrophy of the distal lower limb muscles. These are the exam findings of peripheral neuropathy. His history also supports this pattern. There is enough information here to make the diagnosis, but further testing would possibly help to determine the cause.
The differential diagnosis of this patient’s symptoms is PN, spinal stenosis, radiculopathy, myelopathy and intrinsic spinal cord diseases. For symptoms of numbness or dysesthesia, one might also consider multiple sclerosis or arteriopathy, but the physical exam may easily distinguish these from the others.
The diagnosis of PN can be confirmed by nerve conduction studies (also referred to as EMG). In this particular case, these would probably not add much helpful information. We can observe on exam that the patient has deficits affecting the reflexes, muscles and sensation, so he probably has a so called sensorimotor neuropathy. An EMG can be helpful when the exam is inconclusive, when a different kind of objective evidence is needed, or when radiculopathy and neuropathy need to be distinguished.
When PN is diagnosed, several causes should be considered. In the U.S., certain causes are much, much more common than others. These are: diabetes mellitus, hyperglycemia, vitamin B12 deficiency, alcoholism, trauma and inherited neuropathy. Thyroid disease and uremia may also be a cause of PN. A good proportion of causes of neuropathy prove to be undiscoverable, but we should never assume this will be the outcome before attempting a thorough work up. In rare cases, infection (Lyme disease, HIV, bacterial infection), paraneoplastic diseases (lung cancer, paraproteinemia), toxic chemical exposure (organic chemicals, arsenic), inflammatory diseases affecting nerves, and rare vitamin disorders of various kinds may be worth considering.
Treatment
If the cause of neuropathy is found, it may recover with treatment. Vitamin B12 deficiency may respond to supplementation. Uremia and thyroid disorders are treatable. Treatment of hyperglycemia may lead to improvement in the function of nerves damaged by diabetes mellitus. Patients recover from heavy metal toxicity with removal of the source of the poison and sometimes with chelation therapy. Paraneoplastic neuropathy may improve with the treatment of cancer. Sometimes injured nerves do not respond to these treatments, depending on the severity of the injury.
Patients with peripheral neuropathy may have difficulty walking or using their hands. Treatment by skilled physical and occupational therapists can help them avoid falling, prevent injury and make adaptations to facilitate eating and manual activities. Socks with padded soles or special shoes may be indicated. Regular inspection of the feet is important to prevent painless injuries that lead to infection. The symptoms of pain due to PN may respond to several medications. These include gabapentin, amitriptyline, and pregabalin. Sometimes opioid medication and benzodiazepine medication, spinal cord stimulation and pain interventional procedures are helpful for refractory pain disorders.
Review Questions
- The history or exam of a case of peripheral neuropathy should include which of these features?
a. tingling, numbness and paresthesia
b. diminished sensation in a pattern indicating multiple nerve areas
c. both A and B
d. decreased reflexes
e. hyperglycemia - To help diagnose the cause of PN, you should consider these screening tests:
a. fasting blood sugar
b. serum vitamin B12 level
c. SPEP
d. 24 hour urine heavy metal screen
e. All of the above - Which of these is a best ranking of the frequency of causes of PN, starting with the most common?
a. chemotherapy, alcoholism, diabetes mellitus, idiopathic, vitamin B12 deficiency
b. diabetes mellitus, vitamin B12 deficiency, chemotherapy, idiopathic, inflammatory
c. vitamin B12 deficiency, diabetes mellitus, alcoholism, chemotherapy, idiopathic
d. diabetes mellitus, idiopathic, alcoholism, vitamin B12 deficiency, chemotherapy
e. alcoholism, idiopathic, vitamin B12 deficiency, diabetes mellitus, chemotherapy