Block 5 Neuro Somatosensory Pain MCQ's

The patient's symptoms of hemiplegia on the left side, loss of vibratory sense on the left, and loss of pain and thermal sensation on the right side involving both upper and lower extremities are characteristic of Brown-Sequard syndrome. Brown-Sequard syndrome is caused by a hemisection or damage to one side of the spinal cord. This results in ipsilateral motor deficits and loss of vibratory sense on the same side as the lesion, and contralateral loss of pain and thermal sensation due to the crossing of these pathways in the spinal cord.

The spinal trigeminal tract is responsible for transmitting pain and thermal sensations from the face to the brain. Damage to this structure would specifically explain the loss of pain and thermal sensations on the man's face.

The best localizing sign in this patient is the deviation of the tongue to the left on protrusion. This is indicative of a cranial nerve deficit, specifically involvement of the hypoglossal nerve (CN XII), which innervates the muscles of the tongue. The other findings mentioned in the question, such as weakness of the right upper and lower extremities and loss of sensation on the right side of the body, suggest a contralateral (opposite side) involvement, which is consistent with a medullary infarct. However, the deviation of the tongue is a more specific localizing sign that directly points to the affected cranial nerve.

The loss of pain and thermal sensations on the body below the neck is most specifically related to injury to the anterolateral system. The anterolateral system is responsible for transmitting pain and temperature sensations from the body to the brain. In this case, the infarcted area in the medial area of the pons at the pons-medulla junction, which is consistent with the vascular territory served by paramedian branches of the basilar artery, is likely causing damage to the anterolateral system, leading to the loss of pain and thermal sensations.

The loss of pain and thermal sensations on the right side of the body (excluding the face) suggests damage to the anterolateral system fibers on the left side. The anterolateral system is responsible for transmitting pain and temperature sensations from the body to the brain. Damage to the fibers on the left side would affect the transmission of these sensations from the right side of the body. The other options, such as anterolateral system fibers on the right, anterior trigeminothalamic fibers on the left, medial lemniscus on the left, and medial lemniscus on the right, are not likely to cause this specific pattern of sensory loss.

Damage to type C fibers could elicit loss of pain and temperature sensitivity on the left side of the body. Type C fibers are unmyelinated and transmit slow, dull, and poorly localized pain sensations. They are responsible for transmitting pain and temperature information from the periphery to the central nervous system. Therefore, damage to these fibers would result in a loss of pain and temperature sensitivity on the affected side of the body.

The loss of pain and thermal sensations on one side of the body, excluding the head, suggests a lesion involving the anterolateral system. The anterolateral system is responsible for transmitting pain and temperature sensations from the body to the brain. Lesions in this system can result in a loss of these sensations on the contralateral side of the body. The other structures listed are not primarily involved in transmitting pain and thermal sensations, making them less likely to be the site of the lesion.

The most likely cause of the bilateral loss of pain and thermal sensation on the upper extremities and shoulder in this girl is syringomyelia. Syringomyelia is a condition characterized by the formation of a fluid-filled cyst (syrinx) in the spinal cord. This cyst can compress and damage the nerve fibers responsible for transmitting pain and temperature sensations. The girl's symptoms of not feeling pain or realizing she was cut until she saw blood are consistent with the loss of sensation caused by syringomyelia.

Damage to the medial lemniscus would most likely give rise to the sensory deficits experienced by this patient. The medial lemniscus is a pathway in the brainstem that carries sensory information, including position and vibratory sense, discriminative touch, and proprioception, from the body to the thalamus and then to the somatosensory cortex. In this case, the patient's loss of position and vibratory sense and discriminative touch on the right side of the body below the neck suggests damage to the medial lemniscus on the right side, which is consistent with the infarcted area in the medulla seen on CT.

When you touch the edge of a coin with your right index finger, the tactile information is sent to the cortex by a tract that crosses the neuroaxis at the caudal medulla. The caudal medulla is a region located at the lower part of the brainstem, where sensory information from the body crosses over to the opposite side of the brain. This crossing is known as decussation, and it allows for the integration of sensory information from one side of the body to be processed by the opposite side of the brain.

Damage to the gracile fasciculus on the left would most likely explain the loss of vibratory sensation in the left lower limb. The gracile fasciculus is responsible for transmitting sensory information related to proprioception, vibration, and fine touch from the lower limbs to the brain. Damage to this pathway would disrupt the transmission of these sensory signals, resulting in a loss of vibratory sensation in the left lower limb.

The Romberg's test is used to assess a patient's ability to maintain balance and coordination while standing with their eyes closed. A positive Romberg's test indicates a loss of proprioception, which is the sense of the body's position in space. The major structure that is responsible for proprioception is the dorsal columns of the spinal cord. Therefore, if the Romberg's test is positive, it suggests that the dorsal columns have been affected.

The most likely location of the lesion in this case is the ventral posterolateral nucleus. This is because the patient is experiencing a loss of pain, thermal, vibratory, and discriminative touch sensations on one side of the body excluding the head. The ventral posterolateral nucleus is responsible for relaying sensory information from the opposite side of the body to the somatosensory cortex. Damage to this nucleus can result in a loss of sensation on one side of the body.

The main output cell of the olfactory bulb is the mitral cell. This means that the mitral cells transmit signals from the olfactory bulb to other parts of the brain, allowing for the perception and interpretation of smells. The other statements are not correct in relation to normal olfaction. Primary olfactory neurons are bipolar, not multipolar. Primary olfactory neurons do synapse in specific glomeruli within the olfactory epithelium, but sustentacular cells are not known as basal cells. The olfactory epithelium is located in the superior nasal cavity, not the inferior nasal cavity.

The weakness of the extremities on the right side can be explained by damage to the corticospinal fibers on the left side. The corticospinal fibers are responsible for transmitting motor signals from the brain to the spinal cord, which then control the movement of the extremities. In this case, the infarcted area in the medial area of the pons at the pons-medulla junction, which is supplied by the paramedian branches of the basilar artery, has likely caused damage to the corticospinal fibers on the left side, leading to weakness on the right side of the body.

Meissner's corpuscles are sensory receptors located in the skin that are responsible for detecting light touch and vibration. They adapt rapidly to stimuli, meaning they quickly respond to changes in touch sensation. Additionally, Meissner's corpuscles have a small receptive field, which means they are sensitive to stimuli in a specific localized area. This allows for precise detection of touch and vibration in the skin. Therefore, the correct answer is that Meissner's corpuscles adapt rapidly to stimuli and have a small receptive field.

A lesion of the anterolateral system on the right side would explain the loss of pain and thermal sensations on the left side of the body. The anterolateral system is responsible for transmitting pain and temperature sensations from the body to the brain. When this system is damaged on one side, it results in a loss of these sensations on the opposite side of the body. In this case, the woman's symptoms of numbness on her face and left side of the body indicate a lesion in the anterolateral system on the right side.

After a series of strokes, the woman is experiencing Hypogeusia, which is a reduced ability to taste. The question is asking about the location of the cell bodies of the third-order sensory neurons in the pathway that is affected. The VPM (Ventral posteromedial nucleus) of the thalamus is responsible for relaying sensory information, including taste, to the cerebral cortex. Therefore, the correct answer is VPM (Ventral posteromedial nucleus; of the thalamus).

The correct answer is Mesencephalic. The mesencephalic nucleus is responsible for proprioception and deep sensation in the face, including the jaw-jerk reflex. When the physician taps the mandible, the afferent limb of the reflex is stimulated, and the sensory information is transmitted to the mesencephalic nucleus. Collateral fibers from this nucleus then enter the trigeminal motor nucleus to initiate the motor response, causing the jaw to jerk. The other options, such as Hypoglossal, Principal sensory, and Spinal trigeminal nuclei, are not involved in the jaw-jerk reflex.

Based on the examination findings, the weakness of the left lower extremity suggests a lesion on the left side of the spinal cord. The loss of pinprick sensation on the right side beginning at the T8 dermatome indicates that the lesion is located above the T8 level. Since the lesion is on the left side and above T8, the most likely approximate location is T6 on the left side.

The facial sensory deficits experienced by this woman are explained by a lesion to the axons of cell bodies located in the left trigeminal ganglion. The trigeminal ganglion is responsible for relaying sensory information from the face to the brain. A lesion in the left trigeminal ganglion would result in loss of sensation on the right side of the face, which is consistent with the patient's symptoms.