Step1 Question of the Week #6
A 58-year-old man comes to his physician’s office for a follow up visit. He had an ischemic stroke about two weeks ago and is currently receiving medications for it. He tells his physician that he has recently been experiencing a transient aching pain all over his body, more predominantly on the left side of his body. He goes on to say that he experiences a heightened sense of pain even with the slightest touch. He has observed a change in his response to temperature. He feels warmer than usual even though most of the people in his house are in their sweaters. On examination, he has evidence of left sided gait ataxia along with hemianesthesia of the left side. Motor strength is intact is all four limbs. Examination elicits heightened response to pin prick in the left extremities along with a decrease in vibration sense. There is no loss of sensation detected on the face. Based on the patient’s symptoms, which of the following would indicate the precise location of the patient’s stroke?
(A) Right ventral posterolateral thalamic nuclei
(B) Anterior nuclear group
(C) Left ventral posterolateral thalamic nuclei
(D) Left posteromedial thalamic nuclei
(E) Right ventral anterior thalamic nuclei
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Anterior nuclear group
Correct Option A: The patient is experiencing thalamic pain syndrome also known as Dejerine-Roussy syndrome. A stroke affecting the right ventral thalamic nuclei will result in contralateral pain and hemianesthesia.
The thalamus is a sensory relay for the visual, auditory, gustatory and tactile sensations which eventually reach the sensory cortex in the brain. Basal ganglia and cerebellar motor control also travel through the thalamus. The thalamus is made up of ventral, medial and anterior groups of nuclei. The ventral posterolateral nuclei in the thalamus receives nociceptive and somatosensory information from the medial lemniscus and spinothalamic tracts. This information is then relayed to the primary somatosensory area of the cortex in the parietal lobe.
Dejerine-Roussy or central pain syndrome is due to a resultant lesion in the thalamus. Features of thalamic pain syndrome include a loss of sensation, vibration and position on the contralateral side of the lesion. Patients commonly present with a transient aching or burning pain on the contralateral side of the body. Athetosis and gait ataxia may also be evident. Dysaesthesia (heightened sensation of pain) is characteristic of central pain syndrome, and is a distinguishing feature from sensory stroke, that primarily affects the internal capsule. Thalamic pain cannot be treated with standard anesthetic therapy.
Incorrect Option B: The anterior thalamic nuclei receive information from the mammillary bodies from the cingulate gyrus. One of its main functions is related to episodic memory formation.
Incorrect Option C: Left ventral posterolateral thalamic lesions would result in contralateral thalamic pain syndrome, which is the right side. In the present case, the patient is experiencing symptoms on the left side of the body, the right thalamic nuclei is affected.
Incorrect Option D: The ventral posteromedial nuclei receive information from the trigeminal and taste pathways. Based on the symptoms, there is no mention of loss of taste and facial sensation defects. This information is then relayed to the sensory area of the cortex in the parietal lobe.
Incorrect Option E: Anterior ventral nuclei are motor nuclei in the thalamus. It receives information from the globus pallidus and substantia nigra and relay it to the motor cortex of the brain. It assists with the planning and initiating of movement.
Learning Objective:
The thalamus is a sensory and motor relay to various areas of the brain cortex. Visual, auditory, gustatory and tactile sensations pass through the thalamus to the sensory cortical areas of the brain. The thalamus is divided into the anterior, medial and ventral nuclear groups. The ventral posterolateral nuclei are responsible for receiving spinothalamic and medial lemniscal sensory information. Lesion to this area in the thalamus is responsible for central pain or thalamic pain syndrome. Patients experience a loss of sensation, loss of vibration, position sense all contralateral to the lesion site. Dysaesthesia, a heightened pain sensation is also a characteristic feature.