Diagnostic Pathways for Idiopathic Neuropathy

person in blue shirt wearing brown beanie writing on white dry erase board

“You have a serious illness of an undisclosed nature” says a doctor to a patient in a cartoon within Dr. Norman Latov, MD, PhD’s recent presentation on idiopathic neuropathy sponsored by the Foundation for Peripheral Neuropathy. There are many cases where people present neuropathic symptoms, but the causes are unclear.

Repeated nerve conduction testing may surface more clues as well as nerve and muscle biopsy.

The current diagnostic pathways Dr. Latov maps out are familiar and simple:

  1. Electrodiagnostic (EDX) studies for people presenting the usual clinical symptoms of a neuropathic disease or disorder.
    • If results are normal, do skin biopsies which may reveal axonal damage.
    • If results are abnormal, they will indicate predominantly axonal damage or demyelination.
  2. Test for known causes of either demyelination or axonal damage.
    • If a known cause is identified, it may be treatable or untreatable.
      • Immune mediated:
        • Acute Inflammatory Demyelinating Polyneuropathy (AIDP, Guillian Barre Syndrome, GBS)
        • Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) (Neurological disorder)
        • Multifocal Motor Neuropathy (MMN) (Muscle disorder)
        • MAG Neuropathy (Autoimmune disorder)
        • POEMS Syndrome (Blood disorder)
      • Autoimmune:
        • Axonal Guillian Barre
        • Sjogren
        • Vasculitis
        • Celiac Disease
        • Sarcoid
      • Hereditary Demyelinating or Axonal Neuropathies:
        • Some CMT, dHMN
      • Drug-Induced:
        • Amiodarone
      • Endocrine and Metapbolic:
        • Diabetes
        • Hypothyroid
        • Kidney failure
      • Infectious:
        • Lyme
        • Hepatitis C
        • HIV-1/2
      • Paraneoplastic:
        • Associated with Cancer (Lung, Lymphoma, Myeloma, lgM MOnoclonal Gammopathies)
      • Nutrititional:
        • Alcohol Toxicity
        • B12 or B1 Deficiency
        • B6 Deficiency or Toxicity
      • Toxic:
        • Lead
        • Mercury (Seafood)
      • Drug Induced:
        • Chemotherapy
        • INH
        • Check Point Inhibitors
    • If a known cause is not identified, the “idiopathic” diagnosis remains with no specific treatment.
    • If CIDP is diagnosed, it is treatable.
    • If the neuropathy is stable, it could be residual symptoms from a past insult, GBS, CIDP in remission, Lyme disease, Acute viral illness, Drug or toxin induced, other inflammatory conditions. This is common in small fiber neuropathies.
    • If the neuropathy is progressive, diagnosis can be missed if not tested for. It could be an as yet unidentified genetic mutation, non-systemic vasculitis or sarcoidosis, atypical CIDP not meeting EDX criteria, or primary (light chain) amyloidosis. (Progression is best determined by EDX studies. Sensory symptoms are less consistent and reliable than motor functions. Fluctuating symptoms most often indicate a stable underlying neuropathy and are due to environmental or other factors. Test grip strength, walking speed, and leg strength.)
    • Repeated nerve conduction testing may surface more clues as well as nerve and muscle biopsy.

Dr. Latov is not a proponent of any alcohol use. Previously, alcohol was often thought to be a cause of CMT and other neuropathies, but this was never proven. Dr. Latov is correct, however, that alcohol (especially in significant amounts) is a neurotoxin and doesn’t help anyone’s nervous system apart from the brief, enjoyable effects of intoxication.

Dan Knauss

Dan Knauss

Hi, this is my CMT blog, and I wrote this article. You can read about me and my CMT story. Get in touch if you’d like; I’m always happy to answer questions about CMT and the medical system.

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