Irritation in neck muscles of left side sometimes leading to confusion and hampering in thinking process, sometimes released by stretching but recurrs ?

Mixed symptoms: What you describe might be gently treated by an osteopathic physician (do) skilled in cranial work. Fascial connections can lead to many types of symptoms; good evaluation needed. Osteopathic manipulation is very different from the high velocity "cracks" in chiropractic. You can locate a skilled osteopathic physician through the cranial academy: http://www.Cranialacademy.Org/agreement.Html.