Foraminal (Lateral) Disc Protrusion.

Compression of the exiting L4 nerve root in the neural exit canal without encroachment onto the lateral recess or spinal canal.
A lateral disc protrusion is an important entity to recognise for a number of reasons. First of all it is relatively easy to overlook as it does not impinge upon the spinal canal. Secondly as it does not narrow the subarticular recess it compresses the exiting nerve root only, thus clinically mimicking a posterolateral disc at the level above. As posterolateral discs are common as is multilevel disease, missing a foraminal nerve root compression leading to only one level surgical decompression is a cause of failed back surgery. Additionally as the compression occurs lateral to the normal surgical field, the prospective surgeon needs to be made aware of the protrusion’s location to avoid adequately treating the lateral component.
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References:
1. Medcyclopaedia.com
2. Statdx.com
Credit: Dr Frank Gaillard
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