Neurology: Peripheral Neuropathies Flashcards
Describe Wallerian degeneration in its most basic sense.
When a peripheral nerve is cut, the distal end degenerates and is recycled by the immune system.
Describe the functions of small and large fiber peripheral nerves.
Small Fiber: poorly myelinated, pain and temp sensation, ANS signaling
Large Fiber: heavily myelinated, descriminiative touch, vibration, proprioception, REFLEXES
What are the #1 and #2 risks for polyneuropathies?
- Diabetes Mellitus
2. Alcoholism
Component that causes sensory or autonomic polyneuropathy from overuse of vitamin supplements.
Pyridoxine
Define: hypesthesia, hyperesthesia, dysesthesia, and paresthesia
Hypesthesia - decreased sensation
Hyperesthesia - increased sensation
Dysesthesia - unpleasant, abnormal sensation produced by normal stimulus
Paresthesia - perverted, abnormal sensation like burning, prickling, formication (crawling)
2 conditions that lead to cranial neuropathies.
- Guillain Barre Syndrome
2. Diptheria
5 conditions that lead to ANS neuropathies.
- Diabetes M.
- Amyloid (insoluble fibrous aggregates of protein inside cells, usually neurons)
- Guillain Barre
- Porphyria
- Thallium Poison (rare)
6 conditions that lead to mononeuropathy multiplex.
- Diabetes M
- Vasculitis (from RA or polyarteritis nodosa)
- Trauma
- Plasma Cell Dyscrasia (plasma cell cancers)
- Leprosy
- Sarcoidosis
Describe Guillain Barre Syndrome
Ascending demyelinating motor polyneuropathy often caused by acute inflammation.
Etiology of Guillain Barre
Unknown, leading hypothesis states that the immune system reacts to a cancer or infecitous agents that resembles the bodies nerves and an autoreaction occurs.
Why does Guillain Barre syndrome that results from a Campylobacter jejuni infection take longer to recover than most other forms?
This form of Guillain Barre attacks the axons, not the myelin
What distinguishes Guillain Barre from: 1. Polio 2. Myelitis 3. Botulism in the DDx?
- Polio: bug has been eliminated
- Myelitis: hyper-reflexia, GB has arefelxia
- Botulism: descending motor, GB is ascending
Describe two treatments for Guillain Barre.
- Plasmapheresis: wash the bad Abs out of the blood and return it to patient
- IV IgG: overdose with Abs to shut down the immune system
Describe Uremic Polyneuropathy
Renal failure leads to progressive, painless, symmetrical, sensorimotor polyneuropathy. Patients have parasthesia and restless legs at night.
Treatment can be a renal transplant.
Describe Alcoholic Polyneuropathy
Combination of direct toxicity of alcohol and vitamin deficiency lead to symmetric sensorimotor neuropathy.
Treat with proper nutrition and stop drinking
Most common cranial nerve neuropathy caused by diabetes.
CN VII
Name common symptoms of Autonomic Polyneuropathies.
Genitourinary and Gastrointestinal symptoms, impotence, impaired sweating and vascular regulation
Describe symptoms of a radiculopathy.
PAIN, usually restricted to a dermatome (mostly thoracic) due to poor diabetic control and weight loss.
Describe Amyotrophy.
Painful, proximal leg weakness
Describe the symptoms of the toxic neuropathies caused by:
- Arsenic
- Lead
- Mercury
- Thallium
- Isoniazid
- Mees Lines (on nails), GI and sensorimotor polyneuropathy
- Wrist Drop
- Blindness
- Sensory and autonomic neuropathy, alopecia
- TB medication causes B6 deficiency
Describe Ramsay Hunt Syndrome
Eruption of VZV in the external auditory meatus causing facial paralysis. (like a shingles reaction that occurs in and around the ear)
What is postherpetic neuralgia?
Dysesthetic pain after a shingles outbreak (or any herpetic outbreak). Mainly treated with amitriptyline (anti-depressent) but the pain subsides after a couple days.
Describe the two types of Charcot-Marie-Tooth disease.
Hereditary (autosomal recessive, dominant, or X-linked…so all types of inheritance?). Peroneal muscle atrophy.
Type 1: demyelinating type, stork-leg, foot drop, steppage gait, enlarged nerves
Type 2: axonal type, less severe, atrophy, polyneuropathy
Describe how porphyrias lead to neuropathy.
Abnormal heme metabolism leads to acute MOTOR and ANS neuropathy due to the induced psychiatric issues and seizures.
What is sarcoidosis?
A syndrome involving abnormal collections of chronic inflammatory cells (granulomas) that can form as nodules in multiple organs
What can cause unilateral vs. bilateral Bell Palsy?
Unilateral: Diabetes M, trauma, tumor, stroke, Ramsay Hunt
Bilateral: Myasthenia Gravis, Basal meningitis, sarcoidosis (think systemic conditions)
Both: Guillain Barre, Lyme Disease
First thing to treat when a patient presents with Bell Palsy.
Protect the eye. Patients will not be able to close their eyes.
Next is Prednisone for 1-2 weeks
Main cause of Trigeminal Neuralgia (Tic Douloureux) in young females.
Multiple Sclerosis
Surgical treatment for Trigeminal Neuralgia
Jannetta Procedure: putting a cushion between the nerve and the blood vessels to releive pressure
Trigeminal (Gasserian) ganglion block
Medications used to treat Trigeminal Neuralgia
Seizure meds:
phenytoin, carbamazepine, baclofen
Explain the condition associated with Heterochromia Iridis and why it is indicative of this condition.
Horner Syndrome:
-if a patient presents with two different colored irises, that means that the normal melanocytes (which come from neural crest cells) did not migrate to the iris to produce the normal pigment
-the melanocytes migrate along growing nerves, so if the melanocytes did not make it to the iris, that means that the nerves did not make it either. In the case of Horner Syndrome, the ANS nerves did not migrate to the iris.
Horner Syndrome can be caused by any interruption of the sympathetic nerve pathway. What could interrupt this pathway at:
- T1 nerve root causing a radiculopathy
- Cavernous Sinus
- Superior Cervical ganglion
- Carotid Plexus
- Pancoast Tumor
- aneurysm
- Thyroiditis
- Internal carotid dissection
Name the two tests used to diagnose Horner Syndrome.
- Cocaine Test
2. Paredrine Test (hydroxyamphetamine)
Describe Parsonage Turner Syndrome
Idiopathic Brachial Plexitis -severe pain followed by weakness -involves nerves: Axillary (most common) Long Thoracic Suprascapular Upper Trunk brachial plexus
-Treat with PT and pain meds
What is Saturday Night Palsy?
Compression of radial nerve leading to a radial nerve palsy (wrist or finger drop). Usually happens with intoxicated patients falling asleep with an arm draped over the toilet bowl.
On physical exam, how can a physician differentiate a radial nerve palsy from a stroke causing similar symptoms?
Test the hand grip strength.
Radial Nerve palsy - grip strength intact
Stroke - weak grip strength
Name the muscle that is affected in foot drop and 4 sites of injury that can affect this muscle.
Tibialis Anterior
- Common or Deep fibular nerve
- Sciatic Nerve
- Sacral Plexus
- L5 nerve root
How can you rule out an L5 nerve root injury in a patient that presents with a foot drop?
Ask them to invert their foot. Inversion is done by the tibialis posterior muscle which is also primarily an L5 muscle.
Describe meralgia paresthetica.
Paresthesia or dysesthesia of lateral thigh due to compression of the lateral femoral cutaneous nerve of the thigh.
Describe sciatica.
Paresthesia and dysesthesia following the sciatic nerve innervated areas. It is mainly a radiculopathy of S1.
What distinguishes spondylosis from a disc herniation?
Disc herniations usually involve one level and the pain is short-lived.
Spondylosis involves multiple levels and the pain has long duration.
Describe the 2 main causes of cauda equina syndrome.
- Vascular Ischemia: pain in the legs due to inadequate blood flow to muscles. Weak pulse but regular reflexes.
Neurogenic: either central L4-L5 disc herniation or inflammed ligamentum flavum compressing the vertebral canal. Pulse is normal but the reflexes are diminished.
Describe Raynaud Disease
Episodic blanching of fingers caused by cold or emotions.
Cause is idiopathic but may be due to beta blockers
Effective treatment for Raynaud Phenomenon.
Sympathectomy
Describe causalgia and its treatment.
Trauma to sympathetic nerve fibers resulting in anhydrosis, hair and nail growth impairment.
Treat with procain block or sympathectomy
Describe the 3 stages of Reflex Sympathetic Dystrophy.
- Acute: increased body temp, hair growth and nail growth. Decreased range of motion in the limbs.
- Dystrophic: hyperesthesia, cold intolerance, decreased hair and nail growth, cyanosis
- Atrophic: decreased pain, hyperesthesia, smooth and glossy skin, muscle wasting, contractures
Describe treatment for Reflex Sympathetic Dystrophy.
Treatment in the Acute phase is crucial. Sympathetic block using surgery or meds is effective.
NSAIDs, anti-depressants
