This pain may not be related to the breast cancer though a nerve entrapment in surgical scar may be the cause for pain which may appear on lying down. The other possibility of the diagnosis can be pinched nerves in neck due to herniated or degenerated disc disease. Neck pain may be absent. This frequently appear and worsen on lying. Following investigations may confirm the diagnosis;
1) MRI of the neck
2) Nerve conduction velocity study (NCV)
3) Electromyography (EMG).
The other possibility of the diagnosis is myofascial pain syndromes. These are hyperirritable tender spots in palpable tense bands of skeletal muscle that refer pain. This can be associated with degenerative disc disease in neck causing pinched nerves. Trigger points may develop after an initial injury to muscle fibers. This injury may be a noticeable traumatic event or repetitive microtrauma to the muscles. The trigger point causes pain and stress in the muscle or muscle fiber. The treatment is following;
1) passive stretching.
2) physical therapy; simple muscle stretch, augmented muscle stretch, post-isometric relaxation.
3) deep electrotherapy; iontophoresis, phonophoresis, short wave diathermy, electrical stimulation, high voltage galvanic stimulation, biofeedback.
4) local analgesic patch / ointment / spray
5) anti-inflammatory analgesics; Ibuprofen (Motrin / Advil)
6) ischemic compression therapy; pressure on the points
8) steroid shots
Please feel free for your follow up questions.