Optional medical device diagnostics – depending on the results of the history, physical examination, and obligatory laboratory parameters – for differential diagnostic clarification.
- Sensory/motor electro-neurography (ENG) – to determine nerve conduction velocity:
- Sensory nerve conduction velocity (NLG) of median nerve: > 8 m/s lower than compared to ulnar nerve [method with the highest sensitivity (percentage of diseased patients in whom the disease is detected by using the procedure, i.e., a positive finding occurs)].
- Distal motor latency of the median nerve: > 4.2 m/s (distance 7 cm) [standard measurement due tohigh specificity (probability that actually healthy people who do not suffer from the disease in question are also detected as healthy by the procedure)]
- Prolongation of the distal motor latency of the median nerve compared to the ulnar nerve when derived from the 2nd interphalangeal space > 0.4 ms
- Electromyography (EMG; measurement of electrical muscle activity) of the abductor pollicis brevis muscle – to detect a lesion of the axon (process of a nerve cell).
- High-resolution sonography (ultrasound examination) of the carpal tunnel – to determine the width of the carpal tunnel or tendons; if previously clinically diagnosed by means of CTS-6 (see below “Physical examination”)
- Positive predictive value: sonography: 94%; electrophysiological measurements: 89%.
- Negative predictive value with probability of: Sonography 82%; electrodiagnostics 80%.
- Neurosonography (synonym: nerve sonography; nerve ultrasound); neurologic ultrasound diagnosis; procedure for imaging the peripheral nerve and its surrounding structures.
- Assessment of the cross-sectional area (CSA) of the entire nerve and individual fascicles[detection of pseudoneuroma (focal nerve swelling; nodular thickening of a nerve) anterior to the constriction by means of enlargement of the “cross-sectional area” and flattening of the nerve in the area of the retinaculum flexorum; CSA > 0.11 cm2; reduced echogenicity and mobility of the nerve, increased vascularity]Note: The symptomatology of carpal tunnel syndrome can also be explained by tendovaginitis (tendonitis), which compresses the median nerve due to the associated edema (swelling). In this case, no surgery is required, but anti-inflammatory (anti-inflammatory) treatment.
- X-ray examination of the wrist – if bony cause is suspected.
- Magnetic resonance imaging (MRI; computer-assisted cross-sectional imaging method (using magnetic fields, i.e. without X-rays); particularly well suited for imaging soft tissue injuries) of the arm/hand – if a tumor is suspected.
