Carpal Tunnel Syndrome, Electroneurography, Electromyography, and Statistics

Abstract

For several years, a female 33-year-old patient suffers from numbness and tingling in her right arm and hand, in particular in her index and middle finger. Opening jars has become more difficult, suggesting that the force in her right hand has decreased. Her complaints do not increase when she drives a car or rides a bicycle, nor are the complaints alleviated when she shakes her hand. At night, she incidentally wakes up because of numbness in her fingers. During daytime, the pain in her arm is most prominent. It is already known that she does not suffer from rheumatoid arthritis. The neurological examination does not indicate atrophy of the hand muscles, nor is the force of the abductor pollicis brevis muscle decreased. Her right grasping force is slightly less than normal (MRC 4). The somatosensory function of her hand and fingers is normal. Tapping of the nerves at the wrist does not elicit tingling in the fingers (negative Tinel’s sign), nor does compression of the median nerve in the carpal tunnel by flexion of the wrists (negative Phalen’s maneuver).

Glossary

Abductor pollicis brevis

Muscle used to move the thumb away from the palm of the hand.

Adduction

Movement toward the plane dividing the body in a left and right half.

Anterior horn

(Frontal) grey matter in the spinal cord.

Atrophy

Decrease in muscle volume.

BMI

Body mass index: weight corrected for length as weight/length ²_.

Carpal tunnel

Canal on the inside of the wrist, through which several tendons of lower arm muscles and the median nerve pass on their way from the lower arm to the hand palm.

Distal

Far(ther) from the trunk.

Electrode

Usually a small metal (silver, gold, tin) plate or ring that can be used to record electrical activity. Other forms are needle and sticker electrodes.

EMG power

See power spectrum in Sect. 3.3.3.

Extension

Opposite of flexion: stretching a joint.

Flexion

Bending a joint using flexor muscles.

Hypesthetic

Reduced sense of touch or sensation.

Independent

Here: sampled variables that are already known (e.g., age, length, weight). In contrast, dependent variables depend on independent variables.

Interosseus

Small muscles in the hand palm, used for adducting the fingers toward the middle finger.

Isometric

Muscle contraction which keeps muscle length constant.

Lumbrical

Small muscles in the hand palm, used for flexing and extending hand joints.

Median nerve

One of the main nerves of the arm, another one is the ulnar nerve.

Motor end plate

Region of the muscle membrane involved in initiating muscle fiber action potentials.

Motor neuron

Neuron located in the central nervous system (CNS) that projects its axon outside the CNS to control muscles.

Motor unit

Motor neuron including all muscle fibers it innervates.

MRC

Manual muscle force assessment scale, established by the Medical Research Council in the UK. 0 = no contraction, 1 = flicker or trace of contraction, 2 = active movement with gravity eliminated, 3 = active movement against gravity, 4 = active movement against gravity and resistance, and 5 = normal power. Grade 4 is sometimes divided in 4−, 4, and 4+ to indicate movement against slight, moderate, and strong resistance.

Myopathy

Disease in which (part of) the muscle is not functioning normally, resulting in muscle weakness, cramps, stiffness, and/or spasms.

Neuromuscular junction

Junction of the axon of a motor nerve and the motor end plate.

Neuropathy

Disease in which (part of) the nerve is not functioning normally, resulting in sensory and/or motor disturbances, depending on the damage and the type of nerve (sensory, motor, or mixed).

Proximal

Close(r) to the trunk.

Pyramidal tract

Motor pathway from the cortex to the spinal cord, involved in voluntary skilled movement in particular.

Radial

On the side of the thumb.

Rheumatoid arthritis

Chronic inflammatory disorder, particularly attacking joints.

Temporal dispersion

Here: arrival of action potentials at different moments in time.

Tendomyogenic

Originating from the tendons and muscles.

Tremor

Oscillating movement of one or more body parts.

Thenar muscles

Group of three muscles in the palm of the hand at the base of the thumb.

Ulnar

On the side of the pink.