Hi Wakaday,

Certainly from what you describe there is a structure impinging the nerves supplying those muscles, most likely around C7 level (could be C5->T1). Furthermore it is quitely to be from a disc herniation. However the relatively atraumatic history you describe (as opposed to a whiplash injury for example) is not as common a cause for this type of injury, it is certainly still possible.

From a physiotherapist perspective, there are a number of ways to manage this condition. Personally I would start with McKenzies stretches to try and encourage disc regression and reduce nerve impingement. While I could try and explain these here (they are relatively simple) they are also quite specific and to be honest you are best off to see a physio locally to get a full and proper assessment/explanation.

Prognosis wise, if symptoms dont improve through this conservative management you would be best getting imaging (eg: Wikipedia reference-linkMRI) and maybe an orthopaedic opinion/nerve conduction testing etc but this is looking ahead.

Best of luck

- Greg