TIBIAL MOTOR CONDUCTION STUDY

Tibial motor conduction study is performed by placing active electrode at abductor hallucis brevis (AH) muscle, reference electrode at metatarsophalangeal joint of great toe and ground electrode b/w stimulator and active electrode.
Tibial nerve is stimulated behind medial malleolus and in popliteal fossa. Stimulation of nerve in popliteal fossa is difficult because nerve is lying deep in the fossa.

Usually, a distal latency in excess of 5.0 ms is taken as abnormal. Similarly, CMAP amplitude of less than 5 mv or conduction velocity of less than 40 m/s is taken as abnormal. However, these values may vary b/w various populations, machines etc, thus it is advisable to generate a normative data for each centre.




Reference:

1. Anatomy of Tibial Nerve


2. Routine Nerve Conduction Study


3. MNCS – Parameters


4. Recording Electrodes-For Motor Studies


5. Nerve Conduction Studies – Introduction


6. Recording Procedure-Nerve Stimulation

ULNAR MOTOR CONDUCTION STUDY

Ulnar motor conduction study is performed by placing active electrode at abductor digiti minimi (ADM) muscle, reference electrode about 3 cm distal to active electrode and ground electrode b/w stimulator and active electrode.
Ulnar nerve is stimulated at wrist, below elbow and above elbow. This is because elbow is a common site of nerve damage, thus identifying any evidence of focal demyelination in this segment of nerve is important. Usual evidence of focal demyelination is in the form of conduction block, which is defined as -fall in CMAP amplitude on proximal stimulation in excess of 50%, as compared to distal stimulation. Other evidence is in the form of presence of focal slowing. Identifying these features at elbow, and therefore stimulating the nerve both above and below elbow is important in this study.

Usually, a distal latency in excess of 3.0 ms is taken as abnormal. Similarly, CMAP amplitude of less than 5 mv or conduction velocity of less than 50 m/s is taken as abnormal. However, these values may vary b/w various populations, machines etc, thus it is advisable to generate a normative data for each centre.

Reference:

1. Anatomy of Ulnar Nerve


2. Routine Nerve Conduction Study


3. MNCS – Parameters


4. Recording Electrodes-For Motor Studies


5. Nerve Conduction Studies – Introduction


6. Recording Procedure-Nerve Stimulation

MEDIAN MOTOR CONDUCTION STUDY

Median motor conduction study is performed by placing active electrode at abductor pollicis brevis (APB) muscle, reference electrode about 3 cm distal to active electrode and ground electrode b/w stimulator and active electrode. Median nerve is stimulated at wrist and elbow.

Usually, a distal latency in excess of 3.8-4.0 ms is taken as abnormal. Similarly, CMAP amplitude of less than 5 mv or conduction velocity of less than 50 m/s is taken as abnormal. However, these values may vary b/w various populations, machines etc, thus it is advisable to generate a normative data for each centre.



Reference:

1. Anatomy of Median Nerve
2. Routine Nerve Conduction Study
3. MNCS – Parameters
4. Recording Electrodes-For Motor Studies
5. Nerve Conduction Studies – Introduction
6. Recording Procedure-Nerve Stimulation