NERVE SENSITIVITY – ALTERED NEURODYNAMICS
Detection of abnormal nerve sensitivity is a fundamental part of the clinical examination in musculoskeletal medicine.
Symptoms originating from frank neurological compression (defined as entrapment neuropathies) generally do not pose a diagnostic dilemma and the clinical features of “hard” neurological signs i.e.
are relatively easy to detect.
However subtle neural sensitivity often manifests itself in the absence of hard neurological signs as measured by the classic tests of muscle power, tendon reflex’s and sensory testing. The landmark work of David Butler & Bob Elvey has been central to the integration of neural sensitivity assessment for musculoskeletal clinicians and has give physiotherapists potent weapons in their armoury. Technically speaking, this classification of pain is considered as peripheral neuropathic pain as defined by the International Association for the Study of Pain and is distinct from pain originating from other peripheral tissues because of the nature of the symptoms produced and its response characteristics.
The principals of neural sensitivity testing is with a battery of mechanical provocation tests where the clinician’s objective is to detect mechanical hyperalgesia (an abnormally painful response to a normally non-painful stimulus) by virtue of a positive response to pain provocation testing. These tests are devised along anatomical lines with attempts to either elongate or produce motion i.e. targeting nerve trunk or individual peripheral nerves.
The response is considered abnormal if it either….
reproduces the patient’s pain
reproduces atypical responses associated with nerve sensitivity
or elicits protective responses by virtue of reflex muscle spasm preventing full exploration of the test.
The spectrum of symptoms which may indicate a peripheral neuropathic pain mechanism involve descriptions of symptoms such as….
Lines of pain
Clusters of symptoms along a limb
Sharp shooting stabbing pains
Feelings of compression
Circular “band’s” around particular parts of a limb
Difficult to describe vague sensations (dysaesthesia).
The clinician must be aware of identifying these symptom characteristics and also to identify if they are reproduced or enhanced by neural sensitivity provocation testing neurodynamic testing.
If they are not it may well indicate that the mechanism of pain is still neural but not residing in the peripheral nerve tissue but rather be a central pain state. This again according to the International Association for the Study of Pain is a neuropathic pain mechanism but does not reside in the peripheral tissues and therefore should not be treated as a mechanical phenomenon.
Failure of clinicians to identify non-mechanical mechanisms of symptom generation is a major reason for poor treatment outcomes, poor patient compliance and a low perception of the physiotherapy profession. We must ensure our clinical skills are up to the job.
Enjoy the clinical challenge