The plantar reflex is commonly tested in newborn infants to establish the presence of neuromuscular function. Other superficial reflexes are not commonly tested, though a series of abdominal reflexes can target function in the lower thoracic spinal segments. The spinothalamic pathway decussates immediately upon entering the spinal cord and ascends contralateral to the source; it would therefore bypass the hemisection. The reason for this is that the dorsal column pathway ascends ipsilateral to the sensation, so it would be damaged the same way as the lateral corticospinal tract. Similar to two-point discrimination, but assessing laterality of perception, is double simultaneous stimulation. These fibers travel through the deep white matter of the cerebrum, then through the midbrain and pons, into the medulla where most of them decussate, and finally through the spinal cord white matter in the lateral crossed fibers or anterior uncrossed fibers columns. This means that the sensory deficits will be based on the particular sensory information each pathway conveys.
B It affects only the spinal nerves in the immediate area of the injection. Her frightened parents take her to the emergency room, where she is examined. From the initial neural tube early in embryonic development, the spinal cord retains a tube-like structure with gray matter surrounding the small central canal and white matter on the surface in three columns. These results suggest that Tina has A injured one of her descending nerve tracts. B injured one of her ascending nerve tracts. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful.
The mental status exam contains subtests that assess other functions that are primarily localized to the parietal cortex, such as stereognosis and graphesthesia. E sensory input would be blocked. The sense of position and motion, proprioception, is tested by moving the fingers or toes and asking the patient if they sense the movement. First, the muscles are inspected and palpated for signs of structural irregularities. Whereas the basic sensory stimuli are assessed in the subtests directed at each submodality of somatosensation, testing the ability to discriminate sensations is important. C the spinal cord would not be able to process information at that level. D a spinal injury in the cervical region.
Either the axial musculature will not be affected at all, or there will be bilateral losses in the trunk. Whereas the brain develops into a complex series of nuclei and fiber tracts, the spinal cord remains relatively simple in its configuration. C the spinal cord would not be able to process information at that level. The descending input of the corticospinal tract modifies the response of the plantar reflex, meaning that a negative Babinski sign is the expected response in testing the reflex. To test the sensory fields, a simple stimulus of the light touch of the soft end of a cotton-tipped applicator is applied at various locations on the skin. External Website Watch this to see a quick demonstration of two-point discrimination. The motor system can indicate the loss of input to the ventral horn in the lumbar enlargement where motor neurons to the leg are found, but motor function in the trunk is less clear.
If none of the other subtests suggest particular deficits with the pathways, the deficit is likely to be in the cortex where conscious perception is based. A loss of sensation in his torso B inability to breathe C problems with moving his arms D uncontrollable sweating of his feet E problems moving his legs 40 The preganglionic fibers that connect a spinal nerve with an autonomic ganglion in the thoracic and lumbar region of the spinal cord and carries visceral motor fibers that are myelinated form the A white rami communicantes. Her knee-jerk reflex is normal and she exhibits a plantar reflex negative Babinski reflex. The dorsal, or posterior, horns of the gray matter are mainly devoted to sensory functions whereas the ventral, or anterior, and lateral horns are associated with motor functions. All of these tests are repeated in distal and proximal locations and for different dermatomes to assess the spatial specificity of perception.
The two-point discrimination subtest highlights the density of sensory endings, and therefore receptive fields in the skin. B output to visceral organs would be blocked. D the brain would not be able to communicate with that level of the spinal cord. For the leg, the knee-jerk reflex of the quadriceps is common, as is the ankle reflex for the gastrocnemius and soleus. Touching a specialized caliper to the surface of the skin will measure the distance between two points that are perceived as distinct stimuli versus a single stimulus. B You have no conscious control or modification ability over reflex action.
Her knee-jerk reflex is normal and she exhibits a plantar reflex negative Babinski reflex. D Reflex responses can be enhanced by repetition. Because there is one of each pathway on either side of the spinal cord, they are not likely to interact. An overall loss of strength, without laterality, could indicate a global problem with the motor system. This test can indicate deficits in dorsal column pathway proprioception, as well as problems with proprioceptive projections to the cerebellum through the spinocerebellar tract.
The lateral column, however, conveys both sensory and motor information between the spinal cord and brain. The dorsal column information ascends ipsilateral to the source of the stimulus and decussates in the medulla, whereas the spinothalamic pathway decussates at the level of entry and ascends contralaterally. The trauma would be at the level just before sensory discrimination returns to normal, helping to pinpoint the trauma. An infant would present a positive Babinski sign, meaning the foot dorsiflexes and the toes extend and splay out. The motor exam tests the function of these neurons and the muscles they control.
If the distal locations are not perceived, the test is repeated at increasingly proximal joints. The resulting condition would be hemiplegia on the side of the trauma—one leg would be paralyzed. Failure to recognize two points may be an indication of a dorsal column pathway deficit. While keeping the eyes closed, if the patient unconsciously allows one or the other arm to slowly relax, toward the pronated position, this could indicate a failure of the motor system to maintain the supinated position. The examiner will ask the patient to lift the arm, for example, while the examiner is pushing down on it. Comparison of Upper and Lower Motor Neuron Damage Many of the tests of motor function can indicate differences that will address whether damage to the motor system is in the upper or lower motor neurons. Mistaking painful stimuli for light touch, or vice versa, may point to errors in ascending projections, such as in a hemisection of the spinal cord that might come from a motor vehicle accident.
If one side is not perceived, this may indicate damage to the contralateral posterior parietal lobe. A Reflex responses can change over time. The clasp-knife response occurs when the patient initially resists movement, but then releases, and the joint will quickly flex like a pocket knife closing. The arm is moved at the elbow and wrist, and the leg is moved at the knee and ankle. Testing these stimuli provides information about whether these two major ascending pathways are functioning properly.