T2 RADICULOPATHY

T2 radiculopathy was described by Dr. Deepak Sebastian as a differential screen for radicular pain in the upper extremity. It is a condition where the second thoracic nerve is entrapped in the intervertebral foramen between T2T3 resulting in upper extremity radicular pain.



The anterior divisions of the thoracic spinal nerves from T1 to T11 are the intercostal nerves. They exit from the thoracic spinal column beneath their corresponding vertebra ( O Connor RC, 2002 ). Each nerve is connected with the adjoining ganglion of the sympathetic trunk by a gray and a white ramus communicans. The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum and differ from the anterior divisions of the other spinal nerves in that each pursues an independent course without plexus formation. Lateral cutaneous branches are derived from the intercostal nerves, about midway between the vertebræ and sternum; they pierce the Intercostales externi and Serratus anterior, and divide into anterior and posterior branches. The lateral cutaneous branch of the second intercostal nerve which exits between T2T3, does not divide like the other thoracic nerves, into an anterior and a posterior branch; but midway anterior to the axilla, gives off a branch, the intercostobrachial nerve (ICBN). It pierces the intercostalis externus, the serratus anterior, crosses the axilla to the medial side of the arm, and joins with a filament from the medial brachial cutaneous nerve. It then pierces the fascia, and supplies the skin of the upper half of the medial and posterior part of the arm, communicating with the posterior brachial cutaneous branch of the radial nerve which supplies the lateral forearm (Loukas M 2006). A second intercostobrachial nerve is frequently given off from the lateral cutaneous branch of the third intercostal which supplies filaments to the axilla and medial side of the arm (Fig). One can assume that the ICBN is the communicating link between T2 spinal nerve and the upper extremity. Thus the sequence of events resulting in a T2 radiculopathy involve the T2 spinal nerve, adjoining intercostobrachial nerve, medial antebrachial cutaneous nerve and the posterior brachial cutaneous branch of the radial nerve.

The vulnerability of the upper thoracic spine to mechanical dysfunction is described by various sources (Arana E 2004). As is the case with the lumbar and cervical spine, degeneration of the posterior spinal elements of the thoracic spine is an inherent source of axial back pain and radiculopathy. (Vanichkachorn JS, and Vaccaro AR) suggest generators of thoracic radicular pain to be musculoskeletal, neurological, infectious, visceral, metabolic and congenital. Among the musculoskeletal causes, spondylosis, disc disease and somatic causes have been mentioned. (Edmondston et al) investigated the influence of whole body sitting posture on cervico-thoracic posture, mechanical load and extensor muscle activity in 23 asymptomatic adults. They concluded that the more neutral sitting postures reduce the demand on the cervical extensor muscles and modify the relative contribution of cervical and thoracic extensors to the control of head and neck posture. They suggest postures that promote these patterns of muscular activity may reduce posture related pain suggesting muscle weakness and imbalances to be contributors of neck and upper thoracic pain.

Somatic dysfunction in the upper thoracic region may be postural, or acquired secondary to systemic disorders e.g. asthma. The key contributor to dysfunction is the forward head posture, which comprises upper cervical extension, lower cervical flexion, upper and lower thoracic kyphosis. This could lead to considerable hypomobility of the thoracic spine ( Lounardi AC 2011). The forward head posture is typically associated with weakness of the deep cervical flexors and the thoracic extensors ( Watson Trott 1993). The above factors collectively favor the presence of degenerative and mechanical dysfunction of the upper thoracic region. While upper thoracic spine is vulnerable for degenerative and mechanical dysfunction, the potential for irritation of the intercostobrachial nerve exists, if the T1T2, T2T3 segments are involved, resulting in upper extremity radicular pain. Complaints of upper thoracic pain with pain radiating into the arm, the presence of upper thoracic somatic dysfunction, restricted cervical mobility (especially extension) and pressure mechanosensitivity over the lateral aspect of the thoracic vertebrae causing radiating pain into the arm, may be diagnostic indicators.

REFERENCES:
Arana E, Martí-Bonmatí L, Mollá E, Costa S. Upper thoracic-spine disc degeneration in patients with cervical pain. Skeletal Radiol. 2004 Jan;33(1):29-33. Epub 2003 Oct 22.
Edmondston SJ, Sharp M, Symes A, Alhabib N, Allison GT.Changes in mechanical load and extensor muscle activity in the cervico-thoracic spine induced by sitting posture modification.
Loukas M, Hullett J, Louis RG, Jr., Holdman S, Holdman D. The gross anatomy of the extrathoracic course of the intercostobrachial nerve. Clinical Anatomy. 2006; 19:106-111.
Jennifer W et al. Atypical Chest Pain: Evidence of Intercostobrachial Nerve Sensitization in Complex Regional Pain Syndrome. Pain Physician 2009; 12:329-334
O'Connor RC, Andary MT, Russo RB, DeLano M.Thoracic radiculopathy. Phys Med Rehabil Clin N Am. 2002 Aug;13(3):623-44.
Vanichkachorn JS, Vaccaro AR. Thoracic disk disease: diagnosis and treatment. J Am Acad Orthop Surg. 2000 May-Jun;8(3):159-69. Review.
Watson DH, Trott PH. Cervical headache: an investigation of natural head posture and upper cervical flexor muscle performance. Cephalalgia. 1993 Aug;13(4):272-84; discussion 232.
Sebastian D. T2 radiculopathy: A differential screen for upper extremity radicular pain. Journal of manual and manipulative therapy. 2011; Abstracts of the American Academy of Orthopaedic Manual Physical Therapists (AAOMPT) annual conference, Anaheim, California.
Sebastian D. T2 radiculopathy: A differential screen for upper extremity radicular pain. Phys Theory Pract (publication in process).
 

TRIANGULAR INTERVAL SYNDROME

Triangular Interval Syndrome (TIS) was described by Dr. Deepak Sebastian as a differential diagnosis for radicular pain in the upper extremity. It is a condition where the radial nerve is entrapped in the triangular interval resulting in upper extremity radicular pain. The triangular interval is the space that is triangular in shape, situated between the long head and lateral head of the triceps brachii and the teres major.

The radial nerve and profunda brachii pass through the triangular interval and are hence vulnerable. The triangular interval has a potential for compromise secondary alterations in thickness of the teres major and triceps (McClelland 2007). They described based on cadaveric studies that fibrous bands were commonly present between the teres major and triceps. When these bands were present, rotation of the shoulder caused a reduction in cross sectional area of the space. Normal resting postures of humeral adduction and internal rotation with scapular protraction may be speculated as a precedent for teres major contractures owing to the shortened position of this muscle in this position. In addition, hypertrophy of this muscle can occur secondary to weight training and potentially compromise the triangular interval with resultant entrapment of the radial nerve (ABY Ng et al 2003).

Shoulder dysfunctions have a potential for shortening and hypertrophy of the teres major. Shoulders that exhibit stiffness, secondary to capsular tightness, contribute to contracture and hypertrophy of the teres major (Jiu-jenk Lin 2006). Hence, restricted external rotation can encourage adaptive shortening and thickening of the internal rotators of the shoulder principally the teres major and subscapularis. One may speculate that the lateral arm pain presented in shoulder dysfunctions may be of a nerve origin secondary to adverse neural tension of the radial nerve.

The triceps brachii has a potential to entrap the radial nerve in the triangular interval secondary to hypertrophy. The presence of a fibrous arch in the long head and lateral head further complicates the situation. Repeated forceful extension seen in weight training and sport involving punching may be a precedent to this scenario (Manske 1977, Prochaska 1993, Ng 2003). The radial nerve is vulnerable as it passes through this space, for all of the reasons mentioned above. Awareness of the potential existence of this condition may assist clinicians in their clinical decision making process.

REFERENCES:
Sebastian D. Triangular Interval Sydrome. A differential diagnosis for upper extremity radicular pain. Physiother Theory Pract. 2010 Feb;26(2):113-9.
Ng ABY, Borhan J, Ashton HR, Misra AN, Redfern DRM. Radial nerve palsy in an elite bodybuilder. Br J Sports Med 2003;37:185-186.
McClelland D, Paxinos A. The anatomy of the quadrilateral space with reference to quadrilateral space syndrome. J Shoulder Elbow Surg. 2007 Nov 9
Jiu-jenk Lin, Jing-Lan Yang. Relaibility and validity of shoulder tightness measurement in patients with stiff shoulders. Manual Therapy. 2006; 11 (146-52).