20 - Peripheral Neuropathy Flashcards
Define neuropathy
Neurologic pathology entailing the peripheral nervous system, either sensory and/or motor. Occurring at any point from the anterior and/or posterior root ganglion
What are the three general forms of neuropathy?
- Segmental demyelination
- Axonal degeneration
- Wallerian degeneration
What is segmental demyelination?
- The selective loss of individual myelin internodes with preservation of the axon.
- After demyelination, the remaining Schwann cells can proliferate and remyelinate.The axons.
- However the reconstituted myelin sheaths are both thinner with a shorter internodal length
What is Wallerian degeneration?
- Occurs after transection of the axon.
- Proximally the axon will degenerate back to the node of Ranvier, with possible chromatolysis of the cell body
- Distally the axon and its myelin sheath disintegrate and are digested by the Schwann cell.
What is axonal degeneration?
- Occurs when dysfunction of the neuron renders it unable to maintain its axon.
- The degeneration begins at the peripheral terminal of the axon, and proceeds toward the cell body, there is often chromatolysis of the cell body.
- If the dysfunction can be halted regeneration and recovery of nerve function can occur.
What are the classifications of neuropathies?
Main etiologies
- DIABETIC
- ALCOHOLIC
- NUTRITIONAL
- GUILLAIN-BARRE
A lot of times alcoholic and nutritional can be in the same category
What are some other classificaitons that exist?
Others…
- TOXIC
- HEREDITARY
- RECURRENT
- AMYLOIDOSIS
- PORPHYRIA
- INFECTIOUS
- SYSTEMIC
- TUMOR
Describe the different types of symptoms you will see in a patient with neuropathy
- Motor paralysis
- Tendon reflexes
- Fasciculations and cramps
- Sensory loss
- Paresthesias and dysesthesias
- Sensory ataxia and tremor
- Deformity and trophic changes
- Autonomic disorders
Describe motor paralysis
Persistent impairment of motor function over weeks, or months signifies segmental demyelination, axonal interruption, or destruction of motor neurons
A feature of most polyneuropathies is the distribution (muscles of the feet and legs affected first and most severely.)
*** REMEMBER: Feet and legs mostly **
This is because the nerves are longest going to the legs
Describe tendon reflexes
Loss of reflexes is an invariable sign of peripheral nerve disease and can be diminished out of proportion to weakness
Describe fasciculations and cramps
Neuromyotonia: a state in which the affected muscles ripple and quiver and occasionally cramp.
Use of the muscles increases this activity and there is a reduction in efficiency. Which the patient experiences as stiffness and heaviness
What types of sensory loss will we see?
Tends to affect the distal segments of the limbs, preferably in the legs
Pattern 1 and Pattern 2
Describe pattern 1 of sensory loss
Pattern 1: loss of touch pressure, vibratory, two point-discrimination, and joint position sense as the disease worsens (larger fibers effected more) then the disease progresses proximally and includes loss of pain and temp sensation
Describe pattern 2 of sensory loss
Pattern 2: primary loss of pain and temp with a lesser impairment of pressure, vibratory, and position sense (smaller fibers effected more)
Describe paresthesia and dysesthesias
PARESTHESIA
- Tend to be very prominent in the hands and feet. (Tingling, electric, novacaine like sensations are the most common paresthesias) which is very hard to treat
- Other paresthesias are extremely painful. ( Have the quality of aching, sharp-cutting, or crushing) which is easier to treat
DYSESTHESIAS
- Perversion of sensation is usually characterized by tingling, or burning pain induced by tactile stimuli. (Stimuli will also radiate and persist after the stimulus is withdrawn.)
Describe sensory ataxia and tremor
- Proprioceptive deafferentation with retention of a reasonable degree of motor function is the basis of ataxia of gait and limb movement.
- Tremor of fast-frequency, action type may also appear during certain phases of polyneuropathy
These patients may need assistive devices so they don’t fall and break their hip, etc.
Describe deformity and trophic changes
Tend to be more chronic in nature
- In a number of chronic polyneuropathies the feet, hands, and spine become deformed
- This occurs when the disease begins during childhood
- Foot deformity-30%
- Spine curvatue-20%
Describe the autonomic disorders
- The two most frequent manifestations are anhydrosis and orthostatic hypertension which occur in small fiber polyneuropathies.
- Other manifestations include un-reactive pupils, lack of tears and saliva, impotence, weak bladder and bowel sphincters.
Describe how you go about diagnosing peripheral neuropathy
- Once it has been established that a disease of the peripheral nerves is present, the nature of its existence is then determined.
- A neuropathic syndrome is determined by its mode of evolution, and its clinical presentation.
Describe the classification of peripheral neuropathies
- Axonal peripheral neuropathy
- Demyelinating polyneuropathy
- Hereditary neuropathies
- Neuropathies with inflammation
- Diabetic neuropathies
- Autonomic neuropathy
- Plexopathy
- Mononeuropathy multiplex
Describe acute axonal polyneuropathy
- ** Associated with alcoholism ***
- Evolves over several days
- Porphyric neuropathy and massive intoxication
- 1-3 days renal and liver failure
- 14-21 days polyneuropathy, progresses for 2-3 weeks then a plateau is reached
- Recovery requires months
Not going to see muscle cramps or quivering, no pain, it is PURELY sensory ***
It will resolve - ACUTE course
Describe subacute axonal poly neuropathy
- Evolves in weeks
- Usually toxic or metabolic
- Tend to be chronic in evolution
- Management involves removing the offending agent or treating the systemic disorder
- Sensory vs. motor deficit dependent upon toxic agent
May be seen in Parkinsons patient’s supplemented with cobalamin/ B6
Chronic axonal polyneuropathy
Progression from 6 months to 60 years
- Absence of positive symptoms mostly a motor deficit, and absence of systemic disorder—genetically determined neuropathy
- Relapsing-remitting motor and sensory deficit
Charact. Similar to CIDP
Autosomal dominant
** Viral agent is typically the cause **
A very non specific disorder
Describe acute demyelinating polyneuropathy
This is DEMYELINATING, not axonal
- Synonymous with Guillain- Barré syndrome
- A virus usually precedes the neuropathy, in the majority of cases****
- Charact: areflexic motor paralysis with a mild sensory disturbance, prognosis is good
- Acute rise of total protein in csp in 1st. week*****
Because there is just an acute rise in CSF proteins, it usually is not even detected because we don’t do that test soon enough
Describe subacute demyelinating polyneuropathy
- Acquired neuropathies
- Tend to be a relapsing and remitting neuropathy
- Clinical features similar to GBS. ( But differs in tempo, course, and absence of discernable events)
- May be induced by diphtheria toxin**
Takes several weeks to develop
Describe chronic demyelinating polyneuropathy
- Encompass a wide variety of disorders
- Present diagnostically as a mixed axonal-demyelinative finding
- Motor and sensory manifestations
- Difficult to determine the primary event (axonal degeneration or demyelination)
Note…
You are NOT going to be tested on those specific classifications because they are so hard to define
What are the hereditary components that can lead to peripheral neuropathy
- Charcot Marie tooth
- Roussy-Levy
