Polyneuropathy: When to Refer to Neurology
Steven Day, M.D., Neurologist
Polyneuropathy is a neurological condition involving pathological damage to the peripheral nerves. Symptoms can range from reduced sensory acuity to inappropriate pain from normal sensory stimuli and may also include tingling or painful sensations such as burning, prickling, or electrical shooting pains.
Unfortunately the prevalence of polyneuropathy continues to increase due to increased incidence of medical conditions which cause polyneuropathy in addition to age-related (senescent) polyneuropathy in the aging population. Therefore it is understandable that the number of patients in primary care clinics with polyneuropathy is increasing. This often triggers a question about whether a particular patient with neuropathy should be seen by a neurologist. This question takes on greater significance in the setting of increased attention to costs of care and increased wait times for specialty appointments.
The high yield evaluation for causes of neuropathy is relatively straight forward: diabetic screening, alcohol-abuse screening, thyroid function testing, B12 and methylmalonic acid levels, and an evaluation for monoclonal gammopathy with serum protein electrophoresis (SPEP) and immunofixation (IFE). Of course diabetes and pre-diabetes are the most common causes of polyneuropathy in the U.S. and most of these patients never need to see a neurologist or have an electrodiagnostic study (AKA EMG/nerve conduction study).
Unfortunately even after thorough and extensive testing the cause of many patients’ neuropathy remains undefined and is labeled as “idiopathic.” This can be 30-50 percent of polyneuropathies depending on the population studied. A portion of these patients may have a hereditary cause and others may have senescent polyneuropathy. The good news is that most patients with idiopathic polyneuropathies have generally benign clinical courses and their conditions are often described as “nuisance neuropathies”. Treatment focuses on symptomatic management of neuropathic pain when the pain interferes with sleep or routine activities.
What clinical features prompt additional concern and warrant specialty consultation? There are a few features which should be considered “red flags”.
Rapid onset: Most neuropathies have an indolently progressive course. One that escalates quickly in severity or anatomical distribution over a period of just weeks to a couple of months deserves additional work up even if the initial evaluation is normal.
Early weakness: Nuisance neuropathies are primarily sensory, distal, and without weakness. Patients will complain of paresthesias or dysesthesias of the toes or distal feet but strength remains intact. Watching a patient walk and having them elevate on toes and heels is a high yield exam technique which compliments direct muscle strength testing.
Asymmetric or proximal weakness: It is rare for a routine neuropathy to cause unilateral, asymmetric (e.g. foot drop and contralateral wrist drop), proximal weakness, or cranial nerve involvement.
Early severe pain: The dysesthesias, hyperpathia and allodynia of neuropathy are the primary reasons that patients seek medical attention and these symptoms will progress over time. However severe pain from the onset is unexpected.
Early gait imbalance: Impairment of proprioception in neuropathy can contribute to gait imbalance and falls and is particularly problematic in older individuals who have additional reasons for poor balance such as deconditioning, joint pain, loss of visual acuity and presbyastasis. However imbalance and other forms of incoordination are unexpected initial manifestations of neuropathy in an individual without such risk factors.
Monoclonal gammopathy: Monoclonal gammopathies are relatively common and increase in prevalence in those over 50 years old. Most of these are monoclonal gammopathies of undetermined significance (MGUS) and some of these patients will also develop an unrelated polyneuropathy. However the presence of a monoclonal gammopathy in a person with polyneuropathy warrants additional attention as this could indicate an autoimmune etiology.
The approach to a patient with polyneuropathy can be initially daunting, however by focusing on the high yield evaluation for causes of neuropathy, treating neuropathic pain when it becomes problematic, and pursuing specialty consultation when encountering red flags, patients will receive evidence-based, appropriate and high quality care.