(1) Rules for evaluation of cervical and cervico-dorsal impairments are as follows:

(a) Muscle spasm or involuntary guarding, bony or fibrous fusion, any arthritic condition, internal fixation devices or other physical finding shall be considered, in selecting the appropriate category, only insofar as productive of cervical or cervico-dorsal impairment.

(b) Gradations of clinical findings of cervico-dorsal impairments in terms of "mild," "moderate" or "marked" shall be based on objective medical tests.

(c) Categories 2, 3, 4 and 5 include the presence of complaints of whatever degree in the neck or extremities.

(d) Bladder and/or bowel sphincter impairments deriving from cervical and cervico-dorsal impairment shall be evaluated separately.

(e) Neck as used in these rules and categories shall include the cervical and adjacent areas.