see: [Rosen peripheral nerve disorders](x-devonthink-item://86D59A3D-CC1E-49AC-A7E9-F75C6FD27044), [Talley & O'Connor - peripheral neuropathy](x-devonthink-item://3D26E9FF-28ED-4E4B-A48C-47F1D85D70BF?page=589) See also: [[Neurovascular assessment]], [[Weakness]] ![[Pasted image 20240308232608.png| AIDP: acute inflammatory demyelinating polyneuropathy (GBS); CIDP: chronic inflammatory demyelinating polyneuropathy; DSPN: distal symmetrical polyneuropathy. a proximal distribution of sensorimotor findings may dominate the clinical picture in paatterns 3, 4, and 5, depending on location of lesions.]] | type | proximal/distal | symmetrical vs asymmetrical | motor vs sensory | prototypical disease | | ---- | --------------- | --------------------------- | ------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | 1 | proximal/distal | symmetrical | sensorimotor<br>motor > sensory | [[Guillain-Barré syndrome\|GBS]] | | 2 | distal | symmetrical | sensorimotor<br>sensory > motor | *Distal symmetrical polyneuropathy*<br>- diabetic distal symmetrical polyneuropathy<br>- alcoholism<br>- HIV<br>- arsenic<br>- amiodarone<br>- thiamine def<br>- pellagra<br>- pyridoxine def<br>- amyloid<br>- MM | | 3 | proximal/distal | asymmetrical | sensorimotor | *radiculopathies and plexopathies*<br>- eg from trauma<br>- brachial plexopathy<br>- lumbosacral plexopathy <br>- herpetic<br>- thoracic outlet<br>- traction injury | | 4 | distal | asymmetrical | sensorimotor mononeuropathy | *isolated mononeuropathy*<br>eg carpal tunnel syndrome, elbow, sciatica, etc | | 5 | distal | asymmetrical | sensorimotor mononeuropathy | - vasculitis, diabetes, lyme disease mononeuropathy | | 6 | distal | asymmetrical | pure motor | *amyotrophic lateral sclerosis* | | 7 | distal | asymmetrical | purse sensory | *sensory neronopathy* (ganglionopathy)<br>- HSV 1,2, shingles<br>- pyridoxine tox | > [!key points] > - ==Most polyneuropathies are characterised by a pattern of distal, symmetrical sensorimotor findings, worse in the lower than in the upper extremities==, with a **stocking-glove distribution of sensory abnormalities** that gradually diminishes as one moves proximally. > - The diagnosis of a specific peripheral neuropathy generally requires confirmatory ancillary testing; *approach in the ED should focus on identifying one of seven categorical patterns* (see above algorithm). > - Diagnostic approach to peripheral neuropathies involves combining three clinical features: (1) right-left symmetry or asymmetry, (2) proximal-distal location, and (3) sensorimotor modalities affected. > - Any patient with ==symmetrical weakness, distributed both proximally and distally, with loss or diminution of deep tendon reflexes== (DTRs) and variable sensory abnormalities should be treated as having [[Guillain-Barré syndrome]]. > - **Respiratory compromise is the primary life-threatening event** seen in some peripheral neuropathies; GBS is by far the most common peripheral neuropathic cause of respiratory arrest. > - The definitive treatments for GBS are *plasma exchange* or *intravenous immune globulin (IVIG)*. > - ==High-level evidence== supports the use of pregabalin, gabapentin, and the serotonin and norepinephrine reuptake inhibitor duloxetine in the treatment of *diabetic distal symmetrical polyneuropathy* (DSPN). > - **ALS** is the most common form of motor neuron disease (MND), and ==diagnosis requires the presence of both upper and lower motor neuron findings== - Radial nerve mononeuropathies are characterized by wrist and finger drop and mild numbness over the skin of the first dorsal interosseus muscle. - Humeral shaft fractures are associated with radial nerve injury, with "wrist drop" being the hallmark clinical finding. - The ulnar cutaneous innervation to the hand branches from the main trunk proximal to the nerve entering the Guyon canal. Thus, a lesion at the wrist should not produce sensory abnormalities, whereas one at the elbow would be expected to do so. - The most specific finding for carpal tunnel syndrome (CTS) is splitting of the sensation on the fourth digit (i.e., normal sensation of the ring finger on the ulnar palmar side with abnormal sensation on the median \[radial] palmar side of the same finger). - Lateral femoral cutaneous mononeuropathy (meralgia paresthetica) is caused by injury to this pure sensory nerve as it passes through or over the inguinal ligament, where it may become entrapped or kinked. - The most striking feature of a complete common peroneal mononeuropathy is footdrop caused by weakness of foot dorsiflexion. - The most common neurologic abnormality in **Lyme disease** is unilateral or bilateral facial nerve palsy, usually occurring within a month of exposure. **Mnemonic**: Peripheral nerve: Toxin-MANIC - Toxins (e.g. tick paralysis, heavy metal) - Metabolic (diabetes) - Autoimmune (GBS, CIDP) - Nutritional (B12) - Infectious (VZV/shingles/lyme) - Compression (CTS)