we discuss median nerve entrapment and the most common entrapment neuropathy of them all, carpal tunnel syndrome (CTS).
Especially as both cervical radiculopathy and thoracic outlet syndrome have pain referral patterns that can reach as far as the hand, knowing the differential features of each condition is paramount to a successful assessment.

NERVE INJURIES & NORMAL MOVEMENT

Entrapment neuropathy has been defined throughout the literature as an “isolated peripheral nerve injury which occurs at specific locations where a nerve is mechanically constricted in a fibrous which deformed by a fibrous band”
 Entrapment neuropathies are a “press-induced injury caused by anatomic structures or pathologic processes” Where the peripheral nerves may become subject to compression, tension/stretch, friction or any combination.
 Nerves to do simply stretch. Their movement is a combination of sliding, compression, elongation, convergence and bending…….. Each layer of the nerve has a separate role in each of these functions.
Layers of nerve :
  • Tension occurs in the perineum of the nerve. Nerves can sustain 8-22% elongation before failure with venous blood flow becoming restricted at 8% and occluded at 15%. So stretching nerves isn’t a good idea.
  • Sliding is another movement that occurs in the mesoneurum and allows for dissipation of tension.
  • Compression occurs in the epineurium and can sustain 30-50mmhg before tissue failure
Nerves are particularly sensitive to ischemia. When ischemic changes are due to acute compression the symptoms are reversible. However, when chronic oedema occurs it can leads to scar formation and irreversible changes in the nerve.

CARPAL TUNNEL SYNDROME

The cardinal signs of CTS are pain, paraesthesia and loss of motor control in the distribution of the median nerve. This includes pain, tingling, numbness in the first three fingers but sparing the palm of the hand, weakness of the thumb, loss of grip strength and varying degrees of loss of function.

CLINICAL ANATOMY

CTS is  a sound understanding of anatomy and points of entrapment can greatly assist in clinical diagnosis.
  1. The median nerve arises from the medial and lateral cords of the brachial plexus (C6-T1).
It does not give of motor branches until it reaches the forearm.
  1. In the forearm the median nerve supplies:
  • The flexor/pronator group of muscles – pronator teres, flexor carpi radialis, palmaris longus and flexor digitorum superficialis – not flexor carpi ulnaris.
  • It provides articular branches to the elbow and proximal radio-ulna joint and does not have a sensory distribution in the forearm.
At the elbow, approximately 2 to 5 cm below the medial epicondyle, the median nerve gives off a motor branch called the anterior interosseous nerve which innervates the radial half of flexor digitorum profundus, flexor pollicis longus and pronator quadratus muscles.
The median nerve continues through the forearm and prior to passing through the carpal tunnel the median nerve gives of asensory palmar branch that innervates the central portion of the palm.
Course of median nerve in hand :
The median nerve then travels through the carpal tunnel beneath the flexor retinaculum and gives of a motor and sensory branches to innervate abductor pollicis brevis, opponens pollicis, the superficial part of flexor pollicis brevis and the first and second lumbricals, and sensory branches to the innervate the palmar surface of the lateral three and one-half fingers
Course of the median nerve courtesy of Google Images
For the median nerve specifically, this list outlines the possible points that entrapment can occur:
  • Brachialis muscle,
  • Ligament of struther,
  • Bicipital aponeurosis,
  • Between the Heads of pronator teres,
  • Flexor digitorum superficialis, and
  • In some people between the accessory head of flexor pollicis longus.
 There are other causes of CTS that are not due to entrapment but rather compression due to medical conditions.

CAUSES OF CTS:

Possible etiology includes
repetitive work using the hand and wrist,age,obesitypregnancy,diabetes mellitus, renal disease, thyroid disease, acromegaly, trauma, rheumatoid arthritis and osteoarthritis .
Bordalo Rodrigues et all divided into cause of median nerve into  8 main categories in the research .
  • Neuropathic conditions
  • Inflammatory conditions
  • Metabolic conditions
  • Post traumatic conditions
  • Altered fluid balance
  • Altered anatomy
  • Increased contents of the canal
  • Repetitive hand tasks
  • External pressure
It has been previously documented that there is a strong correlation between the presence of carpal tunnel syndrome (CTS) and diabetes mellitus. In the diabetic population there was a higher prevalence of synovial edema, vascular proliferation and thickening of vascular walls. Diabetes mellitus however, may not be the only endocrine and/or metabolic disorder that increases the prevalence of CTS.
Hypothyroidism is a metabolic condition that occurs when the thyroid does not secrete enough thyroid hormones. “The primary hormones produced by the thyroid are thyroxine, triodothyrone, and calcitonin.” . One of the major symptoms of hypothyroidism is the accumulation of mucopollysaccharides and proteins within the tissues, causing edema. This edema is the resulting cause of compression of the median nerve within the carpal tunnel that results in CTS developing in people with hypothyroidism.
Acromegaly is another consideration and a condition caused by excessive secretion of growth hormones from the pituitary gland that result in enlargement of the hands and feet due to increased bone thickening and soft tissue hypertrophy .
Be sure to question for medical conditions during your subjective assessment and establish if these conditions are being well managed. If not, we are less likely to see success in our treatment because we can’t change these factors with our physiotherapy treatment.

CLINICAL FEATURES OF CTS

During the subjective assessment it is important to listen for the following features .
Image courtesy of Google Images
  1. Primary complaint of paraesthesia or numbness in the hand which involves the first three and a half fingers and the nail beds and distal fingers on the dorsal side.
  2. The patient will report that the symptoms are worse nocturnally.
  3. They might also mention that the symptoms can be eased with vigorous hand shaking.
  4. They may report loss of dexterity with grasping objects and doing up buttons.
It is important to know that the following features are not common symptoms of carpal tunnel syndrome .
(Pain proximal the wrist (can occur but is uncommon)
  1. Whole hand numbness.
  2. Pain which is not involving the first three and a half fingers.
  3. Loss of sensation of the thenar eminence or entire palm.

DIFFERENTIAL DIAGNOSIS:

As mentioned previously CTS presents with pain and P&N in the 3.5 fingers, C6/7 radiculopathy will present with aching pain through the medial border of the scapular and radiating pain along the distribution of the nerve, thoracic outlet syndrome will be more likely to present with mild or aching pain on the ulnar side of the forearm.
Weakness:
  • With cervical radiculopathy weakness will be myotomal.
  • In CTS weakness will be in thumb – abductor pollicis brevis, opponens pollicis, the superficial part of flexor pollicis brevis and the first and second lumbricals.
  • With TOS the hand weakness and clumbiness is present as well as atrophy or guttering of the thenar eminece where Adductor pollicis brevis lies.
Aggravating and easing factors are easier to differentiate.
  • CTS was mentioned previously as nocturnal symptoms and with sustained flexion positions of the wrist.
  • CErvical radiculopathy is aggravating with neck movements and added compression.
  • In TOS there is little to no change in symptoms with neck movements and compression, instead symptoms are agg with palp through the front on the neck above the clavicle
Palpation is another useful examination tool and will require you to palpate the cervical spine and along the course of the median nerve throughout the arm and into the hand, specifically looking at the potential points of entrapment listed above.
don’t forget the usefulness of AROM and PROM test, neurological examination, neurodynamic examination and special tests for
cervical radiculopathy (Spurling and distraction tests),
CTS (Tinel’s sign and Phanel’s test).
SPECIAL TESTS FOR CTS:
Special tests reported in the literature for assessment of CTS is the Phalen’s test and Tinel’s sign.
  • Phalen’s test is described as sustained end of range wrist flexion for at least 60 seconds which is considered positive if hand symptoms are reproduced.
  • The Tinel’s sign is reproduction of pain or symptoms following three taps to the carpal tunnel by the therapist.
Phalen’s test has been shown to have 75% sensitivity ranging from 10 to 91% and specificity ranging from 33-100%.
Tinel’s sign has sensitivity ranging from 23-67% and specificity ranging from 55-100%
Cleland and Koppenhaver (2011) define a positive response as having any one of the following: symptom reproduction, change in symptoms with distant segmental movement or a difference between limbs of >10°. Normal sensory responses may include aching, burning, stretching, or tingling in the medial elbow, the forearm, or hand. Most research looks at specificity and sensitivity in diagnosing cervical radiculopathy with only three known studies assessing this in carpal tunnel syndrome. The sensitivity of the median nerve bias neurodynamic test has been reported between 75-82% (Conevey., 1997; Vanti., 2010; & Wainner., 2005).