Flashcards in OHCM - Mononeuropathies Deck (39):
What helps define the anatomic site of lesions?
Roots of median nerve:
The median nerve is the nerve of ...?
Median nerve - Muscles involved are easier to remember if you use your "LOAF":
Abductor pollicis brevis.
Flexor pollicis brevis.
Median nerve - At the wrist:
Due to lacerations or carpal tunnel syndrome:
1. Weakness of abductor pollicis brevis.
2. Sensory loss over the radial 3 1/2 fingers and palm.
Median nerve - Anterior interosseous nerve lesions:
Due to trauma:
--> Weakness of flexion of the distal phalanx of the thumb and index finger.
Median nerve - Proximal lesions:
Due to compression at the elbow --> May show combined defects.
Ulnar nerve roots:
Ulnar nerve - Vulnerable to ...?
Ulnar nerve - Signs:
1. Weakness/wasting of medial (ulnar side) wrist flexors.
2. Interossei (cannot cross the fingers in the good luck sign).
3. Medial 2 lumbricals (Claw hand).
4. Hypothenar eminence wasting (weak little finger abduction).
5. Sensory loss over medial (ulnar) 1 1/2 fingers and ulnar side of the hand.
6. Flexion of the 4th and 5th DIP joints is weak.
Ulnar nerve - When is the claw hand more marked?
With lesions at the wrist (digitorum profundis intact).
Radial nerve - Roots:
Radial nerve - This nerve ...?
OPENS THE FIST.
Radial nerve may be damaged by compression ...?
Against the humerus.
Radial nerve - Signs:
1. Test for wrist and finger drop with elbow flexed and arm pronated.
2. Sensory loss is variable - Anatomical snuffbox is most reliably affected.
Radial nerve - Muscles involved:
Pain/paresthesiae and weakness in the affected arm in a variable distribution.
Branchial plexus - Causes:
2. Radiotherapy (eg for breast carcinoma).
3. Prolonged wearing of a heavy rucksack.
4. Cervical rib.
5. Neuralgic amyotrophy.
6. Thoracic outlet compression (also affects vasculature).
Consider phrenic nerve palsy if ...?
Orthopnea + raised hemidiaphragm on CXR.
Phrenic nerve lesions - Causes:
1. Lung cancer.
4. Cervical spondylosis/trauma.
5. Thoracic surgery.
6. C3-C5 zoster.
10. Paraneoplastic syndromes.
11. Muscular dystrophy.
12. Big left atrium.
13. Phrenic nerve nucleus lesion (eg MS).
Lateral cutaneous nerve - Roots:
Lateral cutaneous nerve of the thigh - Meralgia paresthetica:
Anterolateral burning thigh pain from entrapment under the inguinal ligament.
Sciatic nerve - Roots:
Sciatic nerve - Etiology:
Damaged by pelvic tumors/fractures to pelvis or femur.
Sciatic nerve - Lesions affect the ...?
Hamstrings + All muscles below the knee (foot drop), with loss of sensation below the knee laterally.
Common peroneal nerve - Originates from ...?
Sciatic nerve just above the knee.
Common peroneal nerve - Signs:
1. Foot drop.
2. Weak ankle dorsiflexion/eversion.
3. Sensory loss over dorsum of foot.
Tibial nerve - Roots:
Tibial nerve - Lesions lead to ...?
1. An inability to stand on tiptoe (plantarflexion).
2. Invert the foot.
3. Flex the toes.
4. Sensory loss over the sole.
Tarsal tunnel syndrome:
Compression of tibial nerve --> Unilateral burning sole pain, eg on walking or standing.
Famous median traps:
2. Enforced flexion (eg in a Colles splint).
3. Diabetic neuropathy.
6. Neoplasms (eg myeloma).
7. Benign tumors (lipomas, ganglia).
10. Pregnancy/premenstrual edema.
Carpal tunnel syndrome - Tests:
1. Neurophysio helps by confirming the lesion's site and severity (and likelihood of improvement after surgery).
2. Maximal wrist flexion for 1min ((Phalen's test) may elicit symptoms (unreliable!).
3. Tapping over the nerve at the wrist induces tingling (Tinel's test; also rather non specific).
Carpal tunnel syndrome - Treatment:
2. Local steroid injection +/- decompression surgery.
3. Many alternative therapies are tried: meta-analyses are doubtful.
The ulnar nerve asks for trouble in ...?
At least 5 places at the elbow:
1. Starting proximally at the arcade of Struthers (a musculofascial band 8cm proximal to the medial epicondyle).
2. And ending distally where it exits the flexor carpi ulnaris muscle in the forearm.
The ulnar nerve - Cubital tunnel syndrome:
Compression occurs at the epicondylar groove or at the point where the nerve passes between the 2 heads of flexor carpi ulnaris (True cubital tunnel syndrome).
Compressive ulnar neuropathies at the wrist are less common ...?
Guyon's canal - Between the pisiform and hamate bones.
--> Can also result in disability.
Hereditary neuropathy with liability to pressure palsies:
An AD hereditary neuropathy presenting as recurrent isolated or multiple neuropathies. Onset is during teenage years.
Neuralgic amyotrophy (Parsonage-Turner syndrome):
A poorly understood inflammatory condition affecting the branchial plexus on one side only.
--> Sudden onset of severe pain, followed over hours by profound weakness, resolving completely over several days.
--> It may rarely involve the phrenic or lower cranial nerves.