Parameters:
(1) thenar atrophy
(2) Phalen’s test (tingling or paresthesia in medial nerve distribution after maximal flexion of both wrists with the dorsum of both hands pressed together for 1 minute)
(3) loss of 2-point discrimination
(4) Tinel’s sign (tingling or paresthesia in medial nerve distribution following repetitive tapping over the carpal tunnel at the wrist)
(5) nocturnal numbness
(6) numbness in the distribution of the medial nerve
|
Parameter
|
Finding
|
Points
|
|
thenar atrophy
|
absent
|
0
|
|
|
present
|
1.44
|
|
Phalen’s test
|
absent
|
0
|
|
|
present
|
1.44
|
|
loss of 2-point discrimination
|
absent
|
0
|
|
|
present
|
1.30
|
|
Tinel’s sign
|
absent
|
0
|
|
|
present
|
1.16
|
|
nocturnal numbness
|
absent
|
0
|
|
|
present
|
1.16
|
|
numbness along median nerve
|
absent
|
0
|
|
|
present
|
1.03
|
X =
= SUM(points for all 6 parameters) – 2.14
probability of CTS =
= 1 / (1 + EXP((-1) * X))
Performance:
• Thenar atrophy (due to muscle atrophy) would seem to be a late finding.
• The agreement between experts and the model was 0.71 which indicates disagreement in almost a third of cases.
• If all of the findings are negative the model gives a 10% chance of CTS.
Items used clinically but not in the model:
(1) comorbid condition (pregnancy, diabetes, hypothyroidism)
(2) improvement with splinting and/or corticosteroid injection
(3) worsening with driving, strenuous hand use or other activity
