Peripheral Neuropathies

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Peripheral Neuropathies

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-diseases which affect the cell body or their peripheral processes
-anterior horn cell at the level of the spinal chord
**patients with PN's do not health well-> important for all fields of medicine
*sensory loss and motor loss usually go together

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Myopathies

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-diseases that effect the muscles

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Neuromuscular Transmission Disorders(NMJ)

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-disorders of the neuromuscular area

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Chief Complaint

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-sensory disturbance with or without weakness
-gait disturbance that can be associated with sensory disturbances (cant feel foot, or has lost proprioception in foot)

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*Pattern in peripheral neuropathies

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*a stocking/glove distribution
*tingling and numbness are worse in feet and in hands
-also, progression of symptoms is very important; our nervous system is precise, so if there is a neuro disorder, there WILL BE A PATTERN

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Small Fiber vs Large Fiber

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-in small fibers, pinprick/temperature sensation will be altered; can also take a skin biopsy to look at neurons
-large fibers, check response to vibration/proprioception

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Weakness Symptoms

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-important to break the symptom down
*cant reach over head->shoulder girdle weakness
*cant get out of chair->hip girdle weakness

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Examination-Weakness

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*again, it's VERY important to establish the pattern
**peripheral lesions will normally have a symmetrical pattern of weakness(stroke will produce asymmetrical)
-does it involve ocular or bulbar mm?
-does it affect breathing?
-distall or proximal weakness?
-what do muscles look like? Atrophy? Hypertrophy?

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Work Up

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-blood work, genetic studies, electrophysiology, biopsy

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Polyneuropathy

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-Subcategory of peripheral neuropathies
-most common; involves many nerves
-can be acquired or inherited

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Mononeuropathy

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-subcategory of peripheral neuropathies
-involvement of one nerve
-Mononeuropathy multiplex
-Radiculopathy

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Mononeuropathy Multiplex

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-summation of multiple single nerve lesions
-causes patches of sensory and motor loss
-pt will start with one nerve involved then gets more
-this is NOT a polyneuropathy
-the pts usually have a disorder of connective tissue such as Lupus or Sjogren's

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Radiculopathy

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-Involves a particular NERVE ROOT
-ex: pt has weakness in biceps and deltoid(C5 root)
-most occur in cervical and then lower lumbar region(L5-S1)

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Plexopathy

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-subcategory of peripheral neuropathies
-involvement of the brachial, lumbar or sacral plexi

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General Clinical Rules in Polyneuropathies

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1. distall muscle affected first! (begins in feet; extensor hallicus longus is first); runs distal to proximal
2. Involves sensory and motor (sensory complaint > weakness)
3. Reflexes are lost in a length-dependent manner! (starts at ankle and goes up); *is bc nerves are affected in a length-dependent manner
4. Pathology is normally due to axonal loss* (myelin loss can also neuropathy, but less frequent)

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Axonal Polyneuropathy

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-most common neuropathy encountered in the US
*longest axons are affected first
-Metabolic: DIABETES (50-70% of pts with DM will develop a PN in their lifetime)
-Toxic: ALCOHOL mainly; also drugs for HIV & cancer
-Infectious: HIV causes a bunch of PN's
-Genetics: CANCER or VITAMIN DEFICIENCIES (B12, FOLATE, and COPPER)

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Mnemonic for causes

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DANG
-diabetes, alcohol, nutrition, Guillaine Barre Syndrome

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Demyelinating Neuropathies

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-much more acute in nature than axonal neuropathies
-Acquired-> Guillaine Barre Syndrome, CIDP
-Inherited-> Charcot Marie Tooth Disease (CMT)

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Guillian-Barre Syndrome(GBS)

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**ACUTE ascending paralysis
-if the course is quick, patients can become totally paralyzed within 24-72 hours (DONT MISS!)
-starts as tingling/numbness in the feet
*can cause respiratory depression and cardiac involvement on an autonomic basis
-body is making antibodies against the myelin

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Chronic Inflammatory Demyelinating Polyneuropathy(CMT)

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--CHRONIC
-almost subacute
-develops over 8 wks

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Charcot Marie Tooth disease (CMT)

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-inherited demyelinating neuropathy
-high incidence in Cajuns
-autosomal dominant disease
*the myelin defect is due to a genetic defect
-pts will present with a distal pattern atrophy, sensory loss, reflex loss and a distal pattern development of weakness; it's progressive
*characteristic signs: hammer toes(toes are curled up), high arches (sign of intrinsic foot muscle weakness); atrophy of the first dorsal interosseous muscle on the hand

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Common causes of Mononeuropathies

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1. Trauma(most common cause); stabbing, MV accident
2. Entrapment or compressive disorder (second most common)
3. Vascular insult
4. Toxic insults

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Carpal tunnel syndrome

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-medican nerve entrapment at the wrist
-abductor pollicis brevis not working

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Cubital tunnel syndrome

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-ulnar nerve entrapment at the elbow
-cant straighten 4th and 5th digits

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Guyon's canal syndrome

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-ulnar nerve entrapment at the wrist
-purely motor symptoms bc all sensory fibers have branched off

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Radial neuropathy

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-radial nerve entrapment
-aka "Saturday night palsy"; fell asleep with your radial nerve entrapped where it goes through the spiral groove
-cant extend fingers

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Peroneal Neuropathy

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-most commonly due to peroneal nerve entrapment behind the fibular process at the knee
-see this in overweight pts who cross their knees a lot...compresses peroneal nerve
-is known to cause foot drop in pts who spend extended periods in the ICU(knee pressed against railing)
-ganglion cysts called "Baker's cysts" behind popliteal fossa can develop and compress the peroneal n.