Dear 123rich

I dont see what you need help with in diagnosing this problem...I think you might be on the mark with your diagnosis

some amount of neck rotation will occur with reaching forward... extension rotation will close the Wikipedia reference-linkfacet joints likely compressing a nerve root, the distribution of the pain suggests C5-C6 (if pain is radiating down the hand to fingers, then maybe lower brachial plexus)
Neural signs such as parasthesia also agrees...the fact that his pain is intermittent is a good thing....

I just have a few suggestions to make to the good reasoning you have done so far

My questions are extension and rotation? what sides preciptates the symptoms...same side or other side?
same side would suggest a facet joint pathology from compression, other rotation will suggest a herniated disc problem or perhaps traction injury to the brachial plexus

What happens with just pure extension and flexion?

it might be unneccessary to do any upperlimb tension tests if the symptoms are pointing to a facet joint pathology primarily because they are uncomfortable for the client and why put them through uneccessary discomfort if the clinical picture is clear...

A few pointers might make it easier to rule out any of the above of include any of the above differentials ive suggested

Traction injuries are unlikely going to give intermittent pain, the pain will most likely always be there and movements that seperate theneck from the shoulder will aggravate even more...id be wary of a distribution that covers serveral dermatomal areas i.e C6, C7,T1 etc...extending to fingers inner side of arm...because this might suggest a herniated disc that is large or several discs out of place at once. In this instance I would refer to a specialist, especially if the client is also having some muscle weakness that is progressive...

If its a cervical disc as would be the case if flexion aggravates or if rotation or rotation/extension aggravates away from the side of the problem, however it can present like a facet joint issue if the disc herniated is large and its pinched by the movement of extension rotation to the same side...again if there is a progressive muscle weakness/numbness...I would refer to a specialist

My experience with facet joint syndromes are that they are more likely in the middleaged to older clients (not exclusively except that in this client, arthritic changes already makes them susceptible)...is your client young? indirect trauma from below as in the outstretched arm can transmit forces to the neck causing the cervical vertebrae to be mal aligned predisposing to narrowing of the facet joints...

I would not conclude yet that it is a facet joint problem until i have explored the other differentials...

Cheers