Occipital Knob Morphological Variations in Human Dried Skulls and Clinical Perspectives
Prominent external occipital protuberance is called occipital knob or spur or occipital bun. Though it was a persistent feature of early modern Europeans, it is extremely rare in the present modern era. Occipital spur was found to be one of the characteristic features of the ancestral Neanderthal trait. Variant anatomy of occipital region forms differential diagnosis in conditions associated with unexplained occipital pain. The present study has been done to evaluate the different morphological forms of occipital knobs. 56 skulls including partial and complete skulls were examined in the department of Anatomy. Broken and incomplete skulls were excluded from the study. 5 8.92 skulls were found to exhibit different forms of occipital knobs. 3 skulls had type 1 flat occipital knob. Type 2 crest and type 3 spine variants have been observed in one skull each. An inca bone was found coincidentally in a skull with flat type of occipital knob which also had three accessory emissary foramina located near foramen magnum. The skull with crest type of occipital knob had two accessory emissary foramina at the external occipital crest and near foramen magnum. Knowledge of variant occipital knobs is an example of application of basic sciences in clinical correlation, one of the goals of the new competency based medical education. Though asymptomatic, discomfort in the occipital region due to occipital spur has to be notified in the differential diagnosis. When symptomatic it could be one of the etiology of occipital headache, mandating surgical excision. To conclude, our study presents occipital knob which is a rare variant of occipital bone near external occipital protuberance that exhibited three forms flat, crest and spine. Coincidentally inca bone and accessory emissary foramina near foramen magnum also have been observed.
Enlarged external occipital protuberance, occipital knob, occipital pain, accessory emissary foramina
Dr. Neelima. P | Dr. R. Ravi Sunder