**2. Upper extremity entrapment neuropathy**

Entrapment neuropathies can occur in both the upper and lower limbs [3]. Entrapment neuropathies of the upper limbs are quite common. Among these, the most common is Carpal tunnel syndrome, then Cubital tunnel syndrome and then ulnar neuropathies [11, 12]. Although anatomical distributions of symptoms differ, these neuropathies contain a similar pathophysiology and treatment [13]. The nerves that innervate the upper extremity originate from the brachial plexus. The brachial plexus begins to form in the posterior cervical triangle and from here extends to the axilla where peripheral nerves are formed that will innervate the upper extremity [14]. After the peripheral nerves responsible for upper extremity innervation leave the brachial plexus, they first lie in the arm region and then in the forearm region. As the nerves course from the arm area to the forearm, they pass through relatively stable structures such as tunnels at the level of the elbow joint. These tunnels are affected by swelling in various clinical conditions such as kidney failure, diabetes, thyroid disease, or a fracture in the area, and cause compression of the travelling nerve. This situation affects the microvascular blood flow, leading to focal ischemia of the nerve. These pathophysiological processes manifest as pain, paresis, loss of sensation and muscle weakness in the areas where the nerve is distributed in the patient [13].

## **2.1 Etiology**

External and internal factors play a role in the etiology of entrapment neuropathies. Anatomical features of the path in which the peripheral nerve travels, the movement pattern of the region where the nerve is compressed, some systemic and local diseases (rheumatoid arthritis, myxedema, acromegaly, synovitis, tenosynovitis, etc.), trauma, space-occupying lesions, incorrectly applied splints, corsets, casts and crutches external are within the factors. However, diabetes mellitus, uremia, avitaminosis and alcoholism are internal factors [5, 15].
