Diabetic and Alcohol-induced Polyneuropathies

00:02 Let's talk a little bit more about diabetic polyneuropathy which is particularly common, and one I would like you to have a good understanding of.

00:09 This presents most commonly as a distal symmetric sensorimotor polyneuropathy.

00:14 So that's how patients describe it.

00:15 And that's what we're evaluating on both our history and our physical exam.

00:19 Sensory manifestations are more common than motor and this presents is a dying back phenomenon with a stocking glove distribution of signs and symptoms.

00:29 It begins distally and progresses more proximally with time.

00:34 This is primarily due to axonal degeneration, but there are varying degrees of demyelination.

00:40 And that is important, we think about demyelination and demyelinating features on the nerve conduction and EMG as suggestive of an inflammatory process.

00:48 But diabetes is one of those conditions where we see prominent axonal findings on the nerve conduction study, some mild demyelinating features and that should not get us off track with working up or evaluating an immune-mediated disorder and evaluating and treating diabetes.

01:05 Here we may see effects on peripheral primarily sensory as well as autonomic nerves.

01:11 And so that involvement of autonomic nerves presenting with orthostasis or constipation can also signal a potential diagnosis of diabetes.

01:19 The distal portions of sensory and autonomic nerves are unmyelinated and can be affected by this underlying process.

01:27 Lack of myelin creates susceptibility to damage in these patients.

01:32 Now let's talk about alcohol-induced polyneuropathy.

01:35 This is one of the three most common causes of neuropathy in the United States.

01:39 Occurs in 40% of patients who are chronic alcoholics primarily axonal in nature, a lot of these toxic metabolic polyneuropathies are axonal and alcoholism is a good example of that.

01:51 Sensory symptoms predominate, motor weakness can occur.

01:55 This begins with symptoms in the lower extremity, upper extremity involvement is often seen later in the course of the disease and sometimes an ataxia or problems with cerebellar function can co-occur with this condition.

02:08 Autonomic neuropathy is often present and may lead to orthostasis or other autonomic symptoms.

02:16 Contributing factors include direct or indirect toxic effects of alcohol.

02:20 Alcohol has both direct effects on the health of the nerves, as well as indirect effects through nutritional deficiency.

02:27 Thiamine deficiency is not uncommon in chronic alcoholics and should be evaluated and treated in patients with a concerning clinical presentation or history.

02:37 Inability to metabolize thiamine in the presence of alcohol is also a consideration in these patients and should be treated and managed.

02:45 How do we work up a patient with a new chronic onset polyneuropathy? What's the work up for a toxic metabolic neuropathy? Well, in general, I like to think about evaluating the most common, the most treatable and then some rare causes of polyneuropathy.

03:02 And you can see here a breakdown in the diagnostic work up recommended for patients presenting with these neuropathic complaints.

03:09 First of all, we consider laboratory testing.

03:13 Blood urea nitrogen and creatine and are used to evaluate for uremia.

03:17 A fasting glucose, random glucose or A1c can be a good screen for diabetes.

03:23 But in those were testing as normal, oral glucose tolerance testing is required to fully evaluate for underlying diabetic neuropathy given the high prevalence and frequency of diabetic neuropathy.

03:36 Thyroid testing is important as well as looking for vitamin B12 deficiency and folate deficiency.

03:43 RPR testing for underlying syphilis, HIV testing can be considered in patients who with a potential risk factors.

03:51 And in men over the age of 50, we think about evaluating for an M-spike with serum protein electrophoresis, urine protein electrophoresis, immunofixation, or a kappa free light chains or free light chain testing in the urine.

04:05 That's more common in men over the age of 50.

04:07 And we think about testing for a paraproteinemia or elevation of an M-spike in those patients.

04:14 In addition, we can consider provocative testing, electrodiagnostic studies to evaluate the underlying neuropathy.

04:22 EMG and a peripheral nerve conduction velocity study can be helpful in determining whether this is axonal and the majority of toxic metabolic neuropathies are axonal or demyelinating.

04:33 There are some rare toxic metabolic conditions that can present with demyelinating features.

04:38 Diabetes would be the most common but there are some other.

04:41 But prominent demyelinating features should suggest an inflammatory etiology and prompt further work up.

04:48 And then lastly, there are some rare causes of polyneuropathy and we can test those in patients where the history or various findings on physical exam suggest the possible rare disorder.

04:59 ESR/CRP testing can be a screen for a systemic autoimmune condition that may be affecting the nerves.

05:05 Vitamin B6 toxicity, Vitamin E deficiency can present with neuropathy.

05:10 Paraneoplastic testing may be needed in patients where we suspect the cancer.

05:14 Importantly, paraneoplastic neurologic disorders can present prior to the onset of cancer.

05:19 So in patients with neuropathy without an underlying diagnosis of cancer, we may need to consider a paraneoplastic origin.

05:26 Urine porphyrins could evaluate a porphyric neuropathy and heavy metal screen for patients who may have heavy metal toxicity.