HY lecture notes:
Carpal tunnel syndrome
Will show up as “median nerve entrapment” as the answer on FM forms –> characterized by pain and paresthesias of the thenar eminence and lateral 3.5 digits.
CTS is normal in pregnancy (edema) and can also be seen in hypothyroidism (edema + GAG deposition) and acromegaly (growth of tendons).
USMLE will not ask you how to Dx CTS, but they’ll sometimes describe the diagnostic maneuver being performed in a vignette:
Dx is with flick sign, Phalen maneuver, Tinel sign, and median nerve compression test (Durkan test).
Flick sign –> patient awakens in pain and shakes out hand to relieve Sx –> 93% sensitive and 96% specific for CTS.
Phalen maneuver –> flexion of the wrist to 90 degrees for one minute elicits Sx.
Tinel sign –> tapping over the carpal tunnel induces Sx.
Median nerve compression test (Durkan test) –> compression of carpal tunnel with the thumbs for 30 seconds elicits Sx.
Treatment (really important for FM):
- Avoid the provoking activity if at all possible (e.g., typing all day in an office).
- Wrist splint (super HY; FM loves conservative therapy first).
- Triamcinolone (corticosteroid) injection into the carpal tunnel (NOT the same as IV steroids). This provides relief for about one month and delays the need for surgery in severe cases for about one year.
- Endoscopic + open nerve decompression are performed if conservative therapy fails after 4-6 months. Never choose these as answers on the USMLE.
Vignettes will sometimes say the patient has tried acetaminophen or NSAIDs to no avail. Recent literature says that these drugs have not been proven to be effective for CTS. On FM NBMEs, I have only ever seen wrist splint and triamcinolone injection as answers for CTS.
Cubital tunnel syndrome
Ulnar nerve entrapment at the medial elbow (proximal entrapment) –> produces paresthesias in along the ulnar distribution of the medial forearm, hypothenar eminence, and medial 1.5 fingers –> classically caused by sleeping with the hands behind the head with the arms bent; can also be caused by bench pressing.
Tx is with a straight-arm cast to be worn while sleeping (this is HY for the USMLE).
Guyon canal syndrome
Ulnar nerve entrapment at the wrist (distal entrapment) –> caused by hook of hamate fracture or chronic handlebar compression in avid cyclists.
Meralgia paresthetica
Numbness and burning pain in the lateral thigh –> due to compression of the lateral femoral cutaneous nerve.
De Quervain tenosynovitis
Pain along the radial aspect of the wrist caused by thickening of the tendon sheaths of extensor pollicis brevis and abductor pollicis longus –> classically seen in breastfeeding women due to long periods of keeping the wrist in a cocked position.
Dx is with Finkelstein test (HY) –> (main picture for this lecture) –> 1) place thumb in the palm of hand, 2) wrap four remaining fingers over the thumb, 3) then ulnar deviate the wrist. If the patient experiences pain at the lateral wrist when attempting the ulnar deviation, that is a positive Finkelstein test and is consistent with a diagnosis of De Quervain tenosynovitis.
The literature says splinting, NSAIDs, and steroid injection are all acceptable as first-line treatments. On the USMLE, a one-off steroid injection into the wrist will be the answer.
In contrast (and as discussed above), wrist splinting will indeed by the first answer in carpal tunnel syndrome, and NSAIDs are not effective in CTS.
