Peripheral Neuropathy Flashcards
Large fiber damage
- Sensory loss (vibration, proprioception)
- Tingling sensation
- Loss of balance (particularly in dark or “challenging situations”, like a boat)
- Hyperreflexia
- Tremor
- Weakness
- Muscle wasting
- Fasciculations
- Cramps
Small fiber damage
- Loss of temperature and pain sensation
- Anesthesia dolorosa “painful loss of pain sensation” OR alodynia
- “Burning” pain
- Pruritis
- “Cold feet”
- Orthostatic hypotension
- Erectile dysfunction
- Constipation
- Urinary retention
- Resting tachycardia
- Postprandial nausea
Mononeuritis multiplexa
Multiple isolated dermatomal neuropathies
“Distal” vs “Length dependent”
Length dependent is mostly in the feet, then in the fingers when it reaches the knees
Distal is hands and feet
Non-length dependent, more demyelinating, more motor involvement tells you. . .
. . . more likely to be autoimmune or infectious than toxic or metabolic
Other elements of Carpal tunnel syndrome
May result in numbness all the way to the shoulder. This does not happen in other nerve entrapment syndromes.
Wrist flexors are innervated by the median nerve.
Foot “slapping” while walking
Foot drop
Peroneal nerve
Ability to stand on toes is dependent upon the ___
Ability to stand on toes is dependent upon the plantarflexors
Steppage gait
Gait associated with foot drop
Basically, the foot can’t hold itself up, so the knee needs to go higher to keep the foot from dragging
Chronic leg crossing may result in. . .
. . . permanent peroneal injury and foot drop
Slimmer’s paralysis
After weight loss, patient can cross legs again
So they do it a lot, cause it’s comfy
But then they get peroneal injury and foot drop
Cab driver’s solute
C7 radiculopathy
Spurling’s test
Test for radiculopathy
Must be done with the head in the direction of suspected radiculopathy with the neck sightly extended. One side at a time.
___ pain is involved in every cervical radiculopathy
Shoulder blade pain is involved in every cervical radiculopathy
Thumb/index finger dermatomes
C5-C6
Middle finger dermatome
C7
Ring/pinky finger dermatome
C8-T1
Other Myasthenia gravis antibodies
MuSK and LRP4
in addition to the classic AChR
Ice pack test
For myasthenia gravis
Alleviates symptoms
Where do we often see myasthenia gravis first and why?
The eyelids, as ptosis
Because these are a fairly weak muscle that is in tonic contraction at rest.
In new onset myasthenia gravis, ___ is helpful even if ___ is not present
In new onset myasthenia gravis, thymectomy is helpful even if thymoma is not present
While myasthenia gravis is purely motor, Lambert-Eaton myasthenia syndrome can have:
- Sensory symptoms
- Cerebellar symptoms
- Autonomic symptoms
- encephalitis
Most common malignant association of Lambert-Eaton myasthenia
SCLC
Acute symptomatic treatment for Lambert-Eaton myasthenia
3-4 DAG
Mixed upper + lower motor neuron signs
Amyotrophic lateral sclerosis
Lateral sclerosis because there is a UMN injury, amyotrophic because there is no hypertrophy due to a coexisting LMN injury.
Genetic cause of ALS associated with ALS
90% of ALS is sporadic
But, a couple of heritable causes are chr 9 ORF 72 repeat expansion and superoxide dismutase-1
Things that ALS spares
Ocular movements
Bowel
Bladder
Study often ordered to investigate suspected plexopathy
EMG/NCS
Really helpful given the less-than-straightforward anatomy of the plexi
Diabetic amyotrophy
Characteristic lumbar plexopathy that affects diabetic patients
It affects the thighs, hips, buttocks and legs, causing pain and muscle wasting.
Diagnosing Carpal tunnel syndrome
- While Tinel’s sign and Phalen’s maneuver can be helpful exam techniques, they are neither sensitive nor specific enough to be definitive
- Definitive diagnosis requires EMG/NCS, though these may be normal in mild carpal tunnel
- Ultrasound can show impaired nerve movement and swelling of the nerve
- Blood tests are useful if you think someone has secondary CTS (amyloidosis, scleroderma, etc)
Treating Carpal tunnel syndrome
- Treatment should begin early after symptoms present
- Initial treatment: Rest the affected hand and wrist for 2 weeks and immobilize the wrist with a splint (especially at night). B6 (pyridoxine) supplementation. Palliate with cool packs, NSAIDs.
- If significant edema is present, diuresis can relieve symptoms
- Immediate relief or refractory disease in non-surgical candidates: Injected or oral corticosteroids
- PT and OT consult – but avoid active exercise while symptoms last
- Refractory disease OR significant atrophy: Surgery (or corticosteroids if non-surgical candidate)
Full list of surgical indications in the setting of carpal tunnel
- Refractory to medical therapy
- Improvement with steroids with recurrence whenever steroids wear off (steroid-sparing)
- Significant atrophy of median nerve innervated muscles
- Persistent sensory impairment/intractable pain
- Mechanical etiology (mass effect)
Recovery from carpal tunnel surgery takes. . .
. . .months
If surgery fails to improve carpal tunnel syndrome, then. . .
. . . a source of systemic neuropathy or another etiology should be sought
What muscles classically atrophies in CTS?
The thenar muscle group, which provides oppositional force in the thumb
What is the main ddx for carpal tunnel syndrome?
C7 radiculopathy
Most common compressive neuropathy of the lower extremity
Compression of the peroneal nerve at the fibular head, causing foot drop and steppage gait
The peroneal nerve runs more superficially near the fibular head, making it vulnerable to direct insult (surgical procedures, compression boots, knee braces).
Note, however, that the ddx for peroneal palsy is quite broad (much more broad than carpal tunnel), and so you need to have a high degree of suspicion for secondary causes unless a clear etiology is present.
Diagnosis of peroneal palsy
- EMG-NCS is extremely helpful in all cases.
- Other studies depend on suspicion for various etiologies
- Posttraumatic or anatomic dysfunction: plain film
- Tumor/compressive mass: MRN
Treatment of foot drop
- If foot drop is not amenable to surgery, an ankle-foot orthosis is often used
- Purpose of an AFO is to provide toe dorsiflexion during the swing phase and medial/lateral stability at the ankle during stance
- If direct injury to dorsiflexor muscles, surgery will be required
- If direct injury to the peroneal nerve, direct surgical repair or removal of insult will be required
- If secondary to lumbar disc herniation, lumbar disc surgery should be considered
- If secondary to a cortical lesion (stroke or MS), an electrical stimulation device should be considered
- Gait training and rehab program will be necessary regardless
Pattern of axon loss reinervation
Reinnervation occurs proximal-to-distal at a rate of ~1mm per day
So, nerve injury closer to the target muscle has a more favorable prognosis with more rapid recovery
Foot drop is often a presenting feature of ___ in young children and teenagers
Foot drop is often a presenting feature of Duscehnne’s or Becker’s muscular dystrophy in young children and teenagers
Froment sign
Decreased pinch strength occurs as a result of weakness of the adductor pollicis muscle
Seen in cubital tunnel syndrome.
Occupational risk factors for cubital tunnel syndrome
Occupations that require heavy lifting or hammering
SNRIs for neuropathic pain
Another option to try in addition to gabapentinoids and TCAs
Ex. duloxetine, venlafaxine
Meralgia paresthetica
- Compression of the lateral femoral cutaneous nerve
- Syndrome of numbness/paresthesias over the lateral aspect of the anterior thigh
- Risk factors: Obesity, pregnancy, wearing tight pants or belts
- Exam: Symptoms reproduced by pressure over the inguinal ligament
- Treatment: Weight loss, wearing looser pants/belt, delivery if pregnant
The chemotox homunculus
