Diminished Sensation in a Dermatome of the Arm

CLINICAL DIAGNOSTIC MANUAL

Diminished sensation in a dermatome of the arm refers to the partial or total loss of sensitivity in a specific area of the arm that is innervated by a particular nerve root.

Each posterior nerve root along the spinal cord is responsible for sensation in a specific region of the skin, known as a dermatome.

Injuries to these roots can result from various pathologies and manifest clinically with numbness, tingling, and reduced sensation in the area corresponding to the affected dermatome.

Pathology	Clinical Symptoms and Signs	Suspected Diagnosis	Confirmatory Diagnosis
Posterior root injury of C5	Diminished sensation in the shoulder and lateral part of the arm, possible weakness in the deltoid	Medical history, neurological examination, radicular pain in C5	Cervical MRI, nerve conduction studies
Posterior root injury of C6	Diminished sensation in the lateral part of the forearm and thumb, possible weakness in the biceps	Medical history, neurological examination, radicular pain in C6	Cervical MRI, nerve conduction studies
Posterior root injury of C8	Diminished sensation in the little finger and medial part of the forearm, possible weakness in the intrinsic muscles of the hand	Medical history, neurological examination, radicular pain in C8	Cervical MRI, nerve conduction studies
Posterior root injury of T1	Diminished sensation in the medial part of the arm and forearm, possible weakness in the intrinsic muscles of the hand	Medical history, neurological examination, radicular pain in T1	Thoracic MRI, nerve conduction studies
Posterior root injury of T2	Diminished sensation in the upper chest and armpit, possible weakness in the chest muscles	Medical history, neurological examination, radicular pain in T2	Thoracic MRI, nerve conduction studies