The Trouble with the Sensory Examination
November 9, 2009 Leave a comment
Blog Post by J. D. Bartleson MD, Associate Professor and Consultant in the Department of Neurology, Mayo Clinic, Rochester, MN
The sensory examination is problematic for clinicians because all sensory loss – whether it is partial or complete – is subjective. If the patient gives a good effort, one can usually be confident about the presence or absence of motor weakness including eye movements. One can be fairly confident about the presence of muscle atrophy and the presence and type of abnormal muscle tone. One can also be confident about the state of reflexes – deep tendon, pupillary, and corneal, for example. Even mental status testing can be relied upon so long as the patient gives a good effort, and even then, one can often determine if the patient is purposefully providing wrong answers. However, the sensory examination is different in that we must rely on the patient’s report of the diminished perception of a stimulus. Only they can tell us if the touch, pin, vibration, change in joint position, sound, or image is normal or reduced. The patient’s responses to sensory testing can be vague and variable, resulting in widely discrepant findings from one practitioner to another. In contrast to reduced or absent sensation, the presence of a sensory function can be reliably determined. If the patient can always tell pin from touch, whether the tuning fork is vibrating or not, whether the joint is moved up or down, repeat what they hear, and state what they see, we know that they have received and correctly processed the sensory stimulus. We cannot be certain that the sensation is absolutely normal, but we can be confident that it is nearly so. Reduced or absent sensation is determined by the patient’s report. The subjectivity of the sensory examination can be frustrating for the patient and provider alike. However, sensory complaints can be revealing whether or not there are findings on examination. Sometimes the patient’s report of a sensory symptom, such as numbness and tingling in the distribution of a specific nerve or nerve root or the characteristic aura of migraine, can provide a diagnosis in the face of a normal or unhelpful examination.
J. D. Bartleson MD is co-author of Spine Disorders, Medical and Surgical Management