From the Guidelines
Length-dependent sensorimotor polyneuropathy is a neurological disorder characterized by progressive damage to peripheral nerves that begins in the longest nerves of the body and advances in a "stocking-glove" pattern, as described in the most recent guidelines 1. This condition typically starts with symptoms in the feet and lower legs before affecting the hands and arms as it worsens. Patients experience both sensory symptoms (numbness, tingling, pain, or reduced sensation) and motor symptoms (muscle weakness, cramping, or atrophy). The pathophysiology involves damage to the nerve axons or their myelin sheaths, often beginning at the nerve endings farthest from the spinal cord.
Causes and Risk Factors
Common causes include diabetes, alcohol abuse, vitamin deficiencies, toxin exposure, and certain medications. According to the latest standards of care in diabetes 1, individuals with a type 1 diabetes duration ≥5 years and all individuals with type 2 diabetes should be assessed annually for distal sensorimotor polyneuropathy (DPN) using the medical history and simple clinical tests.
Diagnosis and Assessment
The following clinical tests may be used to assess small- and large-fiber function and protective sensation:
- Small-fiber function: pinprick and temperature sensation
- Large-fiber function: lower-extremity reflexes, vibration perception, and 10-g monofilament
- Protective sensation: 10-g monofilament These tests not only screen for the presence of dysfunction but also predict future risk of complications, as noted in 1. Electrophysiological testing or referral to a neurologist is rarely needed, except in situations where the clinical features are atypical or the diagnosis is unclear.
Treatment and Management
Treatment depends on the underlying cause and may include managing the primary condition (like controlling blood glucose in diabetic neuropathy), medications for symptom relief (such as gabapentin, pregabalin, or duloxetine for pain), physical therapy to maintain strength and mobility, and lifestyle modifications. Early diagnosis is important as some forms of polyneuropathy can be slowed or halted if the underlying cause is addressed promptly, as emphasized in 1.
From the Research
Definition of Length-Dependent Sensorimotor Polyneuropathy
- A length-dependent sensorimotor polyneuropathy is characterized by symptoms that begin in the feet and progress to the proximal legs and hands, involving both sensory and motor fibers 2.
- This type of polyneuropathy is often associated with systemic amyloidoses, which can lead to focal, multifocal, or diffuse neuropathies involving sensory, motor, and/or autonomic fibers 2.
Clinical Presentation
- The presenting symptoms of length-dependent sensorimotor polyneuropathy depend on the distribution of nerves affected, and may include neuropathic pain, numbness, and weakness 2.
- In some cases, autonomic neuropathy may also occur, affecting various organ systems such as the cardiovascular, gastrointestinal, and genitourinary systems 2.
Relationship to Other Conditions
- Length-dependent sensorimotor polyneuropathy has been associated with various conditions, including diabetic polyneuropathy 3, 4, amyloidosis 2, and cryptogenic sensory polyneuropathy 5.
- The symptoms and progression of length-dependent sensorimotor polyneuropathy may vary depending on the underlying condition and the specific nerves affected.
Diagnostic and Therapeutic Considerations
- The diagnosis of length-dependent sensorimotor polyneuropathy often involves a combination of clinical evaluation, laboratory tests, and nerve biopsy 4.
- Treatment options may include medications such as antiepileptics, antidepressants, and sodium channel blockers, although the most effective treatment may vary depending on the individual case and the underlying condition 5.