13 Acute Peripheral Neurologic Disorders, part 2 Flashcards
Examples of focal mononeuropathies
Median mononeuropathy (carpal tunnel syndrome)
Ulnar mononeuropathy (cubital tunnel syndrome and guyon’s canal syndrome)
Deep peroneal nerve entrapment
Meralgia paresthetica
Most common systemic cause of noncompressive focal neuropathy
Diabetes
most common form of any focal mononeuropathy
median mononeuropathy or carpal tunnel syndrome
Provocative testing in carpal tunnel syndrome
Tinel’s sign
- detects irritated nerves by percussing over the nerve and eliciting tingling
Phalen’s maneuver
- positive for carpal tunnel syndrome when holding the wrists in flexion for 60 seconds evokes or worsens symptoms
most common ulnar mononeuropathy
Cubital tunnel syndrome
Cubital tunnel is located behind the medial epicondyle at the elbow
Guyon’s canal is bounded by
hamate and pisiform bones
Guyon’s canal syndrome is aka “handlebar palsy”
PE in ulnar mononeuropathy
A positive elbow flexion sign is seen when symptoms recur within 3 minutes of the elbow being held in flexion with the wrist in extension
Froment’s sign
- an inability of the thumb to oppose or put pressure against the index finger
- to perform this test, ask the patient to hold a piece of paper between thumb and index finger.
- If you can pull the paper away or the thumb flexes at the interphaleangeal joint to compensate for weakness of the adductor pollicis brevis, the test is positive
In the patient with suspected cubital tunnel syndrome, consider
C8 entrapment and thoracic outlet syndrome
C8 ENTRAPMENT
- presnece of neck pain and worsening symptoms with neck flexion
THORACIC OUTLET SYNDROME
- worsens with shoulder abduction
the deep peroneal nerve may become entrapped at three locations
- fibular head
- anterior to the ankle joint as it passes beneath the extensor retinaculum (anterior tarsal tunnel syndrome)
- distal to the point in #2
Features of compression of the deep peroneal nerve
- Results from proximal fibular fracture or habitual crossing of the legs
- Patients develop foot drop or numbness of the web between the great and second toes
- Conservative treatment is recommended initially - provide a splint or brace to maintain the foot at a right angle with the leg
What is meralgia paresthetica?
Entrapment of the lateral femoral cutaneous nerve in the inguinal canal.
Entrapment causes numbness and pain of the anterolateral thigh.
On examination, the patient may complain of hyperesthesia in the area of pain, and Tinel’s sign may be evident when percussing ove the anterior superior iliac spine
Remarks on pelvic compression test
Supports the diagnosis of meralgia paresthetica
Turn the patient on his or her side,
compress the pelvis,
and if the patient’s symptoms are relieved after 30 seconds of lateral compression of the pelvis, the diagnosis is confirmed
Examples of plexopathies
Brachial plexopathy
Lumbosacral plexopathy
Cervical plexopathy
Most common site of plexopathy
Brachial plexus, formed by C5-T1 nerve roots
1. Brachial plexopathies generally manifest as weakness first, but pain and paresthesias may also develop
2. The upper trunk is the more common site of involvement, affecting proximal arm and shoulder musculature
Causes of brachial plexopathy include
Trauma (penetrating trauma, humeral neck fracture, severe traction injury, or dislocation
Shoulder reduction
Neoplasm (Pancoast tumor)
Radiation
Surgery
Remarks on lumbosacral plexopathy
- The L1-S4 nerve roots form the lumbosacral plexus
- Causes are less likely traumatic, and **more likely to include radiation, diabetic amyotrophy, AORTIC ANEURYSM, retroperitoneal hemorrhage, or compression from AVM
- Differentials include cauda equina and canus medullaris syndromes
Least common plexopathy
Cervical plexus, formed by the C1-C4 nerve roots
Management is usually nonoperative
Examples of neuromuscular junction disorders
Botulism
Tick paralysis
Inflammatory myopathies
Remarks on Botulism
- affects infants between 1 week and 11 months
- has been implicated as a cause of sudden infant death syndrome
- Toxins irrevesibly bind the presynaptic membrane of peripheral and cranial nerves, inhibiting the release of acetylcholine
Classic presentation of botulism
-
Descending, symmetric paralysis
The muscles first affected are the cranial nerves and bulbar muscles - No sensory deficit and no pain
Important point of differentiation of botulism from myasthenia gravis
Botulism: Pupils are often dilated and nonreactive to light (from anticholinergic effect)
MG does not affect the pupil
Treatment in botulism
Administer antitoxin as soon as the diagnosis is made
Presentation of tick paralysis
Ataxia, then ascending weakness and paralysis without sensory involvement
Perform a complete body search for ticks before initiating treatment for other possible diagnoses
Tick paralysis and GBS are indistinguishable even with nerve conduciton studies.
How to remove ticks
Take hold of the very head of the tick with tweezers and apply gentle steady traction.
If a tick is not found on the skin, use a fine-tooth comb to look through hair.
Disposition for inflammatory myopathies
Admit patients with
- rhabdomyolysis
- respiratory distress
- profound weakness
Otherwise, patients may be discharged with neurology or rheumatology follow-up within 7 days
Examples of subacute and acute-on-chonic peripheral nerve lesions
HIV-assocaited peripheral neurologic disease
CMV radiculitis
Diabetic peripheral neuropathy
Patients in the early stages of HIV infection have greater susceptibility to
GBS
Presentation and treatment is similar as in non-HIV GBS
In the latter stages of AIDS,
CMV may acutely infect the lumbosacral nerve roots, causing a polyradiculopathy or cauda equina syndrome
Evidence of systemic CMV infection, including retinitis, is almost always present
Treatment: IV ganciclovir for 3-6 weeks (may be initiated before definitive dignosis)
most common cause of noncompressive focal neuropathy
Diabetes mellitus
emphasize strict foot care to the diabetic who has already developed neuropathy
