This is most likely due to the pinched nerves in the neck which has caused you the muscle atrophy (loss of muscle mass). This can be due to;
1) Herniated/degenerated disc in neck
2) Cervical spondylosis; bone spurs in the neck vertebrae pressing on the nerves.
Following investigations would be required (if not yet done);
1) X-ray of the neck spine
2) MRI of the neck
3) Nerve conduction velocity (NCV) study
4) Electromyography (EMG)
Following measures would be helpful;
1) Neck care in the activities of daily living.
a) No working on computer for more than half an hour in a single stretch. Same for TV.
b) Monitors and televisions exactly in front (180 degrees).
c) Contour pillow: Should fill the hollow when lying on back or straight. Available over the counter.
2) Cervical Collar or Brace
3) Cervical traction
4) Anti-inflammatory analgesics like Ibuprofen
5) Some physicians do give oral steroids in severe radiculopathy cases, in which pain / numbness / tingling is quite significant.
6) Physical therapy: gradually increasing exercises from passive stretching to active against resistance regime.
7) Electrotherapy in the form of TENS, interferential and laser and ultrasound.
8) Hot fomentation
9) Local analgesic patch / ointment / spray
You can consult following specialists;
b) MD in Physical medicine and rehabilitation
Please feel free for your follow up questions.