Thenar Atrophy Definition, Symptoms, Causes, Treatment, Test, Recovery

Learn all about thenar atrophy definition, symptoms, causes, treatment, test and recovery

Studies have shown that thenar atrophy has a specificity of 90–99 % for this diagnosis; however, the sensitivity of thenar atrophy has been determined to be only 12.6 %. Thenar muscle atrophy and impaired sensibility in the distribution of the median nerve are signs of severe and prolonged median nerve compression.

The median nerve innervates the opponens pollicis (OP) and abductor pollicis brevis (APB). These two muscles make up most of the bulk of the thenar eminence and allow the thumb to perform palmar abduction (thumb opening away from the palm) and rotation for pad to pad prehension. Pressure on, or a laceration of the median nerve, inhibits its ability to innervate OP and APB resulting in weakness and thenar wasting.

Additionally, thenar atrophy can occur if the wrist and hand are immobilized in a cast for several weeks or months. Advanced carpal tunnel syndrome is the most common cause of thenar atrophy. Three muscles, several tendons, and a small area of protective cartilage tissue are found in the thenar region. The muscle group that controls the movement of the thumb is stimulated by a long, vital structure called the median nerve. Most cases of thenar atrophy have to do with problems related to the median nerve. When it is compressed or severed, the resulting lapse of electrical activity in the hand means that the muscles are never exercised; unstimulated muscle tissue wastes away over time.

Thenar atrophy due to any cause is usually very noticeable. There might be an obvious dent in the palm or along the outer edge of the base of the thumb. At rest, the thumb may be fixed in a rigid position across the front of the palm. In cases of severe atrophy, it is impossible to bend or move the thumb at all.

What is Thenar Atrophy?

Diminished or lost innervation of the thenar muscles produces a flattening of the thenar eminence. Because muscles are responsible for opposition and palmar abduction, these motions become significantly weakened or absent resulting in an adducted thumb posture and ultimately the loss of web space length. The functional result is the degradation of fine motor skills involving tip to tip or pad to pad pinch and diminished ability to grip large objects when the ability to open the thumb away from the hand is lost.

Thenar Atrophy Definition

The thenar region of the palm is the group of muscles in the thick pad just underneath the thumb. Thenar atrophy is an erosion of muscle tissue, which can impair control over the thumb and leave the hand disfigured. The problem can be several different conditions and disorders, including carpal tunnel syndrome, acromegaly, or direct trauma to the wrist or thumb.

Thenar Atrophy Symptoms

Pain around the soft muscular rounded part at the base of the thumb is a symptom of thenar atrophy;

• Tightness of thenar eminence.
• A nodule at the base of the thumb along the palmar surface.
• The thumb gets locked after flexing it can be a symptom of thenar eminence pain.
• Neurovascular compression.
• Symptoms of carpal tunnel syndrome.

Thenar Atrophy Causes

Thenar atrophy is caused by a variety of clinical conditions it is commonly associated with carpal tunnel syndrome. Thenar eminence pain is caused due to fine and repetitive nature of work, which leads to chronic overuse of the thumb. Few examples of which include constant typing on mobile phones and laptops, work of a massage therapist, hammering, sewing and so forth. Hormonal changes in women, particularly postmenopausal can be one of the major risk factors of thenar eminence pain.

Thenar Atrophy Treatment

Thenar atrophy treatment depends on the underlying condition, a patient may need to take specialized medications or undergo surgery to decompress the median nerve. Physical therapy is important in the recovery stages to safely and effectively rebuild muscle mass in the thenar region. A healthcare professional may also decide to schedule a clinical electro-stimulation procedure to massage and work the muscles. With treatment, most cases can be reversed.

• A splint can be used for to counteract the loss of both pinch and grip function and provide a significant aid to both fine and gross motor function.
• Secondly, because the thumb assumes an adducted position, there may be a tightening or loss of web space. It is important to consider a splint for night during sleep to maintain the length of the soft tissue in the thenar web space. This splint should be sturdy, but comfortable enough to sleep in and maintain the web space at its optimal length. A custom fabricated orthosis may be called for or a custom fit splint such as the 3pp Thumb Spica Plus that includes a custom moldable insert may be chosen to retain or restore the web space.

Thenar Atrophy Test

The doctor performs physical examination and records medical history and notes down the symptoms experienced by the patient. Further use is made of thenar eminence pressure test and carpel tunnel compression test for routine examination and diagnosing the condition.

• Testing thumb Abduction:-With the palm up and hand resting on table or examiners hand, the patient is instructed to raise his/her thumb perpendicular from the palm as the examiner applies downward pressure to the end of the thumb. This test isolates an important muscle in the thumb that is stimulated by the median nerve.
• Key pinch exam;-The thumb muscle should be tight and firm, because the person is contracting or flexing this muscle as they pinch harder and harder to prevent the paper from slipping.

Thenar Atrophy Recovery

Thenar atrophy recovery may take up-to 6 months. Thenar atrophy was assessed and divided to mild, moderate and severe grade before surgery and at 3 and 6 postoperative-months. Clinical severity, degree of electrodiagnostic abnormalities and demographic data were compared between recovery and non-recovery groups of thenar atrophy. However, thenar atrophy is not always recovered postoperatively, especially in severe cases.