The Peripheral Nervous System Flashcards
What are the signs/symptoms of a peripheral neuropathy affecting the SMALL nerve fibers?
neuropathic pain
disturbed temperature sensation
autonomic dysfunction (arrhythmias, othostatic hypotension, impotence, incontinence, constipation)
What are the signs/symptoms of a peripheral neuropathy affecting the LARGE nerve fibers?
loss of vibration and proprioception
weakness
fasciculations
loss of DTRs
What are some of the common causes of peripheral neuropathies? Mnemonic: VITAMINS
Vitamin deficiency/Vasculitis
Infections (TB, Leprosy)
Toxic (amiodarone, lead, vincristine, chemo)
Amyloid
Metabolic (alcohol, diabetes, porphyria, hyperthyroidism, liver and renal failure)
Idiopathic/Inherited
Neoplasm
Systemic (SLE, polyarteritis nodosa, multiple myeloma)
What are the 4 most common causes of peripheral neuropathy in order?
Diabetes
Alcohol
Non-alcoholic liver disease
Malignancy
What’s the term for a neuropathy that involves several individual nerves in a multifocal distribution?
mononeuropathy multiplex
What is the mortality rate for GBS (Acute inflammatory demyelinating polyneuropathy)?
only 5%
20% of GBS cases in the US are preceded by infection with what?
c. jejuni
others include HSV, CMV, EBV
What are some of the antibodies found in GBS?
most against gangliosides:
anti-GM1 (poor prognostic indicator)
anti-GD1a
anti-GQ1b
anti-GD1b
How does GBS present?
rapidly evolving, ascending areflexic motor paralysis with or without sensory disturbances
often starts with tingling in the feet or with lower back pain
How long does GBS usually take to reach its nadir?
usually 2 weeks, but can be up to a month
There is a variant of GBS associated with fait ataxia, areflexia and external opthalmoplegia, usually without limb weakness. What’s this one called?
Miller-Fisher syndrome
What antibody is positive in 90% of Miller-Fisher cases?
anti-GQ1b
What will you see on CSF analysis in GBS?
albuminocytologic dissociation (high protein but few or no cells)
What will early EMG/NCS studies show in GBS?
prolonged distal latencies
variably prolonged or absent F waves
possible conduction block
decreased motor unit recruitment
Because of the potential for diaphragm involvement, patients are tracked with FVCs. An FVC below what would make you plan to intubate?
less than 15 mL/kg
What is the treatment for GBS?
IVIg or plasmapheresis are equally effective
IV steroids are not beneficial
Describe a typical presentation of chronic inflammatory demyelinating polyneuropathy.
It’s basically chronic GBS
it’s a slowly evolving weakness beginning in the legs with widespread areflexia and loss o vibratory sense (so a large fiber issue)
weakness of neck flexors often present
can have painful paresthesias
they tend to have a chronic course with many relapses
About 90% of CIDP will respond to what?
steroids, but 50% will relapse afterwards
can also do periodic IVIG with weekly or monthly treatments
Describe the typical presentation of multifocal motor neuropathy.
it’s pure-motor multiple mononeuropathy; usually presents with a slowly progressive, asymmetric, predominantly distal limb weakness usually beginning in the arms
you get weakness developing in the distribution of individual nerves instead of following a spinal myotome
What antibody is often found in multifocal motor neuropathy?
IgM anti-GM1
It’s important to distinguish multifocal motor neuropathy from typical motor neuron diseases because MMN will respond will to what treatment regimen?
IVIg, rituximab and immunosuppressants
Is the neuropathy associated with monoclonal gammopathies (multiple myeloma, amyloid, macroglobulinemia, lymphoma, etc) primarily demyelinating or axonal?
demyelinating
Describe the peripheral neuropathy seen in diabetes.
Usually a distal, symmetric, slowly progressive sensory loss in the legs (stocking distribution beginning in the toes and feet before the hands)
autonomic insufficiency is an important feature
weakness is a late feature
Is uremic neuropathy more sensory or motor-predominant?
More motor predominant - foot drop and leg weakness are common features
What is the diagnosis if someone has an acute or subacute sensorimotor peripheral neuropathy that mimicks GBS with abdominal pain?
the neuropathy associated with acute intermittent porphyria
What is the most common inherited peripheral neuropathy?
Charcot-Marie-Tooth
Describe the typical progression of CMT.
Usually adolescents with symmetric, slowly progressive distal muscular atrophy of the legs and feet, eventually involging the hands
hammer toes and pes cavus are common
Most of the CMTs are primarily demyelinating, except which one?
CMT-2 is an axonal motor neuropathy
What’s the diagnosis in an HIV patient with a CMV infection who presents with rapidly progressive flaccid paraperesis, sphincter dysfunction, perineal sensory loss, and lower limb areflexia?
lumbosacral polyradiculoneuropathy
Leprosy is one of the most common causes of neuropathy world-wide. What are the clinical features of the neuropathy?
usually mononeuropathy multiplex with a predilection for cooler areas of the body like the nose, ears or distal limbs
DTRs usually preserved
NERVE HYPERTROPHY that can be palpated
What are some features of autonomic neuropathy?
orthostatic hypotension, diarrhea, constipation, early satiety, tachycardia or palpitations, blurred vision, urinary retention, and erectile dysfunction
What is Pandysautonomia?
it’s an acquired autonomic neuropathy, usually immune in nature following a viral illness in which both the sympathetic and parasympathetic nervous systems are affected
