possible neuralgia?

My brother's been suffering from neck pain radiating to the back of his head. He had undergone MRIs of brain and neck but the findings appeared normal except for straightening of cervical spine secondary to muscle spasm, same findings were found on his EMG - NVC (extremities only), just mild muscle spasm and cervical x-ray shows straightening of cervical spine.

He had been complaining these symptoms everyday for almost 3 months now: pain on the neck radiating to the back of his head, numbing of his head (back portion) and mild numbing of left arm whenever he wakes up. He's got visual disturbances like mild blurring of vision and photosensitivity, he also complains that his eyes feel kind of sleepy everyday. No vomiting, loss of consciousness, hypertension, diabetes noted.

Arcoxia (etoricoxib) had been given and over the counter painkillers, but none seems to respond to alleviate his headache.

We already consulted 3 neurologists unfortunately they can't find any specific cause of it. I suspect that he might have glaucoma but he doesn't manifest the major symptoms of it. I hope someone can relate to this and suggestions and opinions are highly appreciated.