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The thenar eminence is the mound formed at the base of the thumb on the palm of the hand by the intrinsic group of muscles of the thumb. [1] The skin overlying this region is the area stimulated when trying to elicit a palmomental reflex. The word thenar comes from Ancient Greek θέναρ (thenar) 'palm of the hand'. [2]
In medicine, split hand syndrome is a neurological syndrome in which the hand muscles on the side of the thumb (lateral, thenar eminence) appear wasted, whereas the muscles on the side of the little finger (medial, hypothenar eminence) are spared.
The opponens pollicis causes the thumb to flex and rotate medially, leaving the thumb unable to oppose. Carpal tunnel syndrome can result in thenar muscle paralysis which can then lead to ape hand deformity if left untreated. [11] Ape hand deformity can also be seen in the hand of benediction deformity. [citation needed]
The intrinsic muscles of the thumb can be divided into two groups; the thenar eminence and other muscles. The thenar eminence refers to the group of muscles on the palm at the base of the thumb. The three muscles composing the thenar eminence are the abductor pollicis brevis, flexor pollicis brevis and opponens pollicis. [5]
It also supplies the muscles of the thenar eminence by a recurrent thenar branch. [8] The rest of the intrinsic muscles of the hand are supplied by the ulnar nerve. The median nerve innervates the skin of the palmar (volar) side of the index finger, thumb, middle finger, and half the ring finger, and the nail bed.
In the thenar eminence, the recurrent branch of the median nerve provides motor innervation to: [4] opponens pollicis muscle; abductor pollicis brevis muscle; superficial part of flexor pollicis brevis muscle; A separate, more proximal branch of the median nerve additionally provides motor innervation to the 1st and 2nd lumbricals of the hand.
Pain over the hypothenar eminence especially at the ring finger, though all fingers of the same hand may be affected (thumb is never affected); increased sensitivity to cold and reduced sense of touch in affected digits [1] Causes: multiple trauma of the fingers leading to Ischemia., Smoking, type of occupation: example carpenters, polishers ...
A person with idiopathic carpal tunnel syndrome will not have any sensory loss over the thenar eminence (bulge of muscles in the palm of hand and at the base of the thumb). This is because the palmar branch of the median nerve, which innervates that area of the palm, separates from the median nerve and passes over the carpal tunnel.