Thomas Findley MD PhD VA New Jersey Health Care System, East Orange NJ and UMDNJ-New Jersey
Medical School, Newark NJ. Thomas.Findley@va.gov 973 676 1000 x 2713
20% of humans show anatomic variations in nerves (median-ulnar anastomosis in both forearm and hand [5]), muscles (pectoralis abdominis [6]) or vertebrae (extra lumbar and thoracic [1]). While there is variation in numbers of thoracic vertebrae (9 to 23) across species, all mammalian species except two have exactly 7 cervical vertebrae [3]. Cervical ribs are found in only 1% of human adults, but they are found in 40-60% of fetuses with congenital abnormalities, and in children are associated with increased cancer incidence. This is felt to be caused by an underlying genetic defect which causes abnormal Hox gene expression, that gene affecting both patterning of the axial skeleton and tumor suppression [2]. Thus there is a very strong selection against cervical ribs and the associated other congenital abnormalities. The presence of 6 lumbar vertebrae has been reported many years ago [8], with 3% having 6 lumbar, 10% 4 lumbar, 7% 13 thoracic and 3% 11 thoracic vertebrae [7]. There is a great deal of variation in the lumbar plexus. Persons with 6 lumbar vertebrae and a lesion between L5 and L6 can have radicular symptoms at L5, S1, or a combination [4].
CASE: a 39 year old very athletic male presented with left knee and low back pain. Manual therapy, chiropractic and physical therapy exercises gradually resulted in marked improvement in the knee pain but persistent back pain radiating to the big toe.
When manual therapy was followed 24 hours later by chiropractic manipulation, there was movement felt lower in the spine than previously, and back pain resolved. Xrays showed 6 lumbar vertebrae. Review of xrays of his mother also showed 6 lumbar vertebrae.
CONCLUSION: Anatomic variations in nerves, muscles and bones are common. Some have a genetic basis and may be associated with other changes in body physiology, including immune function. Knowledge of common variations assists in planning treatments.
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