Intervertebral Disc Prolapse
NAME OF PATHOLOGY: Intervertebral Disc Prolapse, "Slipped-disc"
Definition: A protrusion of the nucleus pulposus though a weakness in the annulus fibrosus.
Causes: There are numerous bio-mechanisms which have been implicated in the development of disc prolapses. Prolapses tend to affect people aged twenty to fourty in whom the bones have ossified but where the intervertebral discs still have enough water content to prolapse. Causes of disc prolapses include: heavy lifting with inadequate posture and/or morphology, compressive trauma such as parachuting, and jumping from great heights, obesity, and connective tissue disorders. Most prolapses occur postero-lateraly due to the criss-cross lamellae arrangement of the intervertebral discs, and the presence of the posterior longitudinal ligament.
Examination: The extent and location of the prolapse will greatly influence the signs and symptoms manifest in the patient.
Observation: Patients suffering from a disc prolapse will usually adopt an antalgic stance or gait. All ranges of spinal motion may be reduced in an acute presentation, with marked limitation in spinal flexion. It is important to determine whether the patient exhibits any signs of a lower motor neuron lesion (in acute prolapses, the neurological picture may be confused): hyporeflexia, hypotonia, fasciculations, and asthenia. Elucidate any radiating pain as this may be useful in determining the spinal segment(s) affected by the prolapse.
A central disc prolapse may result in cauda equine syndrome: a medical emergency characterised by perineal anaesthesia, urinary retention and post-void residual incontinence, decreased anal tone; and sexual dysfunction.
Orthopaedic tests for disc prolapses:
Valsalva maneuveur: the patient is instructed to forcibly exhale against their closed airways. An aggravation in symptoms indicates a positive.
Slump test: with the patient seated instruct them to slouch whilst looking straight ahead, than instruct them to flex their head, than passively flex their straight symptomatic leg, than introduce ankle dorsiflexion. Each step introduces a sensitising factor. A positive is indicated when any of the above factors causes an aggravation in symptoms.
When testing for a disc prolapse one should also elucidate the integrity of the corticospinal tract (strength), and map out any areas of paraesthesia or anaesthesia. Definitive diagnosis is achieved via MRI.
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