A Woman With Neck Pain and a Weak Arm

A 24-year-old woman presented to her family doctor complaining of difficulty rotating the neck and pain in the left shoulder; she received corticosteroid injections into the neck with some relief. Five months later, she developed left upper extremity pain radiating from the shoulders to the forearm, and she presented to the emergency room because of the increased pain.

Past medical and social histories were unremarkable.

Neurologic examination showed decreased strength of 4/5 in the left triceps and wrist extensors and mild 5−/5 finger extensor weakness. All other upper extremity and lower extremity muscles, including biceps and brachioradialis, were normal. Reflexes were symmetric and normal, except for absent left triceps reflex. Plantar reflexes were flexor. The sensation was intact to pain, vibration, and light touch. Her pain was reproduced when the neck was tilted laterally and slightly rotated and the crown of the head pushed down (Spurling test). The rest of the examination was normal.

What is the Differential Diagnosis?

This woman presented with neck pain and weakness in the triceps and wrist extensor muscles and absent triceps reflex, suggesting a C7 radiculopathy. This was most likely caused by a ruptured disk. Other lesions that can cause radiculopathy are neurofibromas, tumors, vascular malformations, hematomas, spondylosis with bony spurs, and infections, including herpes zoster. The combination of neck pain and muscle weakness makes the diagnosis of a middle trunk, posterior cord, or radial nerve lesion unlikely, particularly as radial nerve-innervated muscles that originate from other roots, such as the brachioradialis (C5–C6), were clinically intact. The foraminal compression on the Spurling test reproduced the pain as it alters the size of the neuroforaminal opening, aggravating nerve irritation. On the other hand, tilting the head in the opposite direction and abducting the symptomatic arm relieve the pain due to opening the foramina.

An EMG Test was Performed

Motor Nerve Studies

Nerve and Site	Latency (ms)	Amplitude (mV)	Conduction Velocity (m/s)
Median Nerve L.	Normal ≤ 4.2	Normal ≥ 6	Normal ≥ 50
Wrist	3.7	12	–
Elbow	8.5	12	53

Ulnar Nerve L.	Normal ≤ 3.6	Normal ≥ 8	Normal ≥ 50
Wrist	2.8	10	–
Below elbow	6.7	10	54
Above elbow	8.7	10	60

Nerve and Site	Latency (ms)	Amplitude (mV)	Conduction Velocity (m/s)
Radial Nerve L.	Normal ≤ 3.5	Normal ≥ 4.4	Normal ≥ 51
Forearm	3.3	6	–
Axilla	6.8	6	63

F-Wave Studies

Nerve	Latency (ms)	Normal Latency ≤ (ms)
Median nerve L.	29.2	30
Ulnar nerve L.	28.8	30

Sensory Nerve Studies

Nerve	Onset Latency (ms)	Normal Onset Latency ≤ (ms)	Peak Latency (ms)	Normal Peak Latency ≤ (ms)	Amp (μV)	Normal Amp ≥ (μV)	Conduction Velocity (m/s)	Normal Conduction Velocity ≥ (m/s)
Median nerve L. (index)	2.4	2.6	2.9	3.1	28	20	54	50
Median nerve L. (middle)	2.2	2.6	2.7	3.1	32	20	59	50
Ulnar nerve L.	2.3	2.6	2.8	3.1	16	13	52	50
Radial nerve L.	1.8	2.6	2.3	3.1	45	30	56	50

EMG Data

Muscle	Insrt Activity	Fibs	Pos Waves	Fasc	Amp	Dur	Poly	Pattern
Cervical paraspinals L.	Inc	2+	2+	None	Norm	Norm	None	Full
Supraspinatus L.	Norm	None	None	None	Norm	Norm	None	Full
Infraspinatus L.	Norm	None	None	None	Norm	Norm	None	Full
Serratus anterior L.	Inc	1+	1+	None	Norm	Norm	None	Full
Deltoid L.	Norm	None	None	None	Norm	Norm	None	Full
Biceps brachii L.	Norm	None	None	None	Norm	Norm	None	Full
Triceps L.	Inc	3+	3+	None	Norm	Norm	None	Red
Flexor carpi radialis L.	Inc	2+	2+	None	Norm	Norm	None	Red
Flexor carpi ulnaris L.	Norm	None	None	None	Norm	Norm	None	Full
Extensor digitorum communis L.	Inc	2+	2+	None	Norm	Norm	None	Red
Extensor indicis proprius L.	Inc	2+	2+	None	Norm	Norm	None	Red
Pronator teres L.	Inc	2+	2+	None	Norm	Norm	None	Full
Pronator quadratus L.	Norm	None	None	None	Norm	Norm	None	Full
First dorsal interosseous L.	Norm	None	None	None	Norm	Norm	None	Full