Sensory System Examination
Overview of the Sensory System Examination
The sensory system examination is a critical component of the neurological assessment, designed to evaluate the integrity of sensory pathways from peripheral receptors to the cerebral cortex. A systematic approach to sensory testing helps clinicians localize lesions and diagnose neurological conditions affecting sensation.
Primary Sensory Modalities
Light Touch
Light touch sensation is tested using a cotton wisp or monofilament applied to the skin. The patient, with eyes closed, indicates when and where they feel the stimulus. This tests the function of large myelinated A-beta fibers and the dorsal column-medial lemniscal pathway.
Pain and Temperature
Pain sensation is assessed using a disposable pin or broken wooden applicator, while temperature sensation is tested with tubes of warm and cold water. These modalities travel via small unmyelinated C fibers and the spinothalamic tract, making them useful for distinguishing between different types of sensory pathway lesions.
Vibration and Proprioception
Vibration is tested using a 128 Hz tuning fork placed over bony prominences. Proprioception (joint position sense) is assessed by moving the digits up or down while they identify the direction of movement. Both modalities are carried by the dorsal columns. Proper coordination and gait examination complements sensory testing in the neurological workup.
Cortical Sensory Functions
Cortical sensory testing evaluates higher-order processing including stereognosis (object recognition by touch), graphesthesia (recognizing numbers traced on the palm), and two-point discrimination. These tests assess parietal lobe function and are valuable for detecting cortical lesions.
Dermatome Testing
Systematic dermatome testing maps sensory deficits to specific spinal nerve root levels. This is particularly important in evaluating radiculopathies, spinal cord injuries, and peripheral neuropathies. ConductScience offers neurological examination tools for clinical and research applications.
Clinical Significance
Patterns of sensory loss provide crucial diagnostic information. A glove-and-stocking distribution suggests peripheral neuropathy, a sensory level indicates spinal cord pathology, and dissociated sensory loss points to specific tract involvement. Integration of sensory findings with behavioral testing paradigms enhances research into neurological conditions.
References
- Campbell, W. W. (2013). DeJong’s The Neurologic Examination (7th ed.). Lippincott Williams and Wilkins.
- Bickley, L. S. (2016). Bates’ Guide to Physical Examination and History Taking (12th ed.). Wolters Kluwer.
- Blumenfeld, H. (2010). Neuroanatomy through Clinical Cases (2nd ed.). Sinauer Associates.
