SENSORY EXAM: ABNORMAL EXAMPLES
Light Touch
With light touch the patient indicates that the perception of the stimulus is different over the left side of the face. The feeling has an abnormal quality to it described as different, uncomfortable or burning. This would be called paresthesia or dysesthesia. Light touch causing pain would be allodynia.
Pain – Upper Extremities
A sharp wooden stick is used to delineate the area of decreased sharp sensation. There is loss over the ulnar side of the right hand as well as the ulnar aspect of the forearm but the arm is normal. This loss is constant with a C8-T1 dermatome distribution.
Pain – Lower Extremities
This patient has a sensory level at T3 with decreased pain sensation below the level including the leg. The sensory level is one to two spinal cord segment levels below the actual anatomical cord lesion because the spinothalamic axons ascend several spinal cord levels prior to crossing. The left sided T3 sensory level combined with this patient's upper extremity sensory finding indicates a lesion of the right side of the spinal cord at the C8-T1 level.
Temperature
The patient is unable to distinguish the difference between a hot and cold test tube simultaneously applied to the ulnar side of the right hand and arm and the left leg. This deficit is in the same distribution as the pain deficit noted when testing sharp sensation. Pain and temperature sensation are tests for spinothalamic tract function.
Vibratory
Vibratory sensation is decreased on the right great toe compared to the left. This could be due to a peripheral neuropathy but it also could be secondary to DCML deficit, which is actually the case for this patient.
Position Sense
The patient makes more mistakes identifying the correct direction of toe movement on the right then left indicating a proprioceptive loss. For this patient this is secondary to a lesion effecting the dorsal column on the right side of the spinal cord.
Tactile Movement
When comparing left vs. right, the patient has more difficulty on the right side again indicating dorsal column dysfunction. If the dorsal column pathways are intact, then tactile movement is a sensitive test of parietal cortical function.
TWO-POINT DISCRIMINATION
Patients with a lesion of the primary somatosensory cortex will have difficulty with two-point discrimination on the opposite side of the body. The peripheral nerve and DCML pathway must be intact for this test to be a test of parietal cortical function.
Graphesthesia
This patient has more difficulty identifying numbers written in the right hand than in the left hand. This is called agraphesthesia and is from a lesion of the somatosensory cortex in the left parietal lobe.
Stereognosis
The patient is asked to identify objects placed in both the right and left hand with his eyes closed. He knows that something is in his right hand but he is unable to identify it while he readily identifies the same object placed in the left hand. This is called astereognosis. The patient has a lesion involving the left parietal lobe.
Double Simultaneous Stimulation
When the patient is touched on the right or left he correctly identifies the side touched but when both sides are touched simultaneously he neglects the stimulus on the right. This is extinction or simultanagnosia and indicates a lesion in his left parietal cortex.