Thalamic Syndrome (Dejerine-Roussy Syndrome)

Definition

Physiology of the Thalamus in Sensation (Guyton & Hall)

"When the somatosensory cortex of a human being is destroyed, that person loses most critical tactile sensibilities, but a slight degree of crude tactile sensibility does return. Therefore, the thalamus (and other lower centers) apparently has a slight ability to discriminate tactile sensation..."

"Conversely, loss of the somatosensory cortex has little effect on one's perception of pain sensation and only a moderate effect on the perception of temperature. Therefore, the lower brain stem, the thalamus, and other associated basal regions of the brain are believed to play dominant roles in discrimination of these sensibilities."

• Guyton and Hall Textbook of Medical Physiology, Chapter 48 (Function of the Thalamus in Somatic Sensation)

• Neospinothalamic (fast pain): Sharp, well-localized pain travels via A-delta fibers to the VPL nucleus, then to the somatosensory cortex.
• Paleospinothalamic (slow-chronic pain): Diffuse, burning pain via C-fibers terminates in reticular formation, intralaminar and ventrolateral nuclei of the thalamus. Only 10-25% of these fibers reach the thalamus directly.

"Electrical stimulation in the reticular areas of the brain stem and in the intralaminar nuclei of the thalamus, the areas where the slow-suffering type of pain terminates, has a strong arousal effect on nervous activity throughout the entire brain."

• Guyton and Hall, Chapter 49 (Paleospinothalamic Pathway)

Thalamic Syndrome - Pathophysiology (Guyton & Hall)

"Secondary hyperalgesia frequently results from lesions in the spinal cord or the thalamus."

• Guyton and Hall, Chapter 49 (Some Clinical Abnormalities of Pain and Other Somatic Sensations)

Thalamic Syndrome - Direct Description (Ganong)

"An infarct in the thalamus can lead to a loss of sensation. Thalamic pain syndrome can occur during recovery from a thalamic infarct. The syndrome is characterized by chronic pain on the side of the body contralateral to the stroke."

• Ganong's Review of Medical Physiology, 26th Ed., Chapter 8 (Effects of CNS Lesions)

Summary of Clinical Features

Key Mechanisms (Synthesis)

1. Initial phase: The thalamic infarct (typically in the territory of the thalamogeniculate artery, supplying the VPL) destroys the relay nucleus for all somatosensory modalities - producing contralateral hemisensory loss for pain, temperature, touch, vibration, and proprioception.
2. Recovery phase: As Ganong notes, during recovery the damaged circuits become aberrantly active. Because the thalamus (not just the cortex) is the primary seat of pain and temperature consciousness per Guyton & Hall, damage here produces spontaneous pain rather than simply a deficit.
3. Chronic pain: The slow-chronic paleospinothalamic pathway terminates in intralaminar nuclei of the thalamus. Damage to adjacent ventroposterior nuclei may disinhibit these intralaminar nuclei, generating persistent, poorly-localized burning pain - exactly the type Guyton & Hall attributes to the slow C-fiber system.

Cause

• Thalamic infarct (most common) - occlusion of thalamogeniculate branches of the posterior cerebral artery
• Thalamic hemorrhage
• Thalamic tumors or demyelination (less common)

• Guyton and Hall Textbook of Medical Physiology - Chapters 48 ("Function of the Thalamus in Somatic Sensation") and 49 ("Paleospinothalamic Pathway," "Some Clinical Abnormalities of Pain," "Hyperalgesia")
• Ganong's Review of Medical Physiology, 26th Ed. - Chapter 8 ("Effects of CNS Lesions," "Thalamic Pain Syndrome")

Thalamic Syndrome - Detailed Review

1. Nomenclature and Historical Background

2. Anatomy - The Relevant Thalamic Nuclei

"The thalamus apparently has a slight ability to discriminate tactile sensation... loss of the somatosensory cortex has little effect on one's perception of pain sensation... the lower brain stem, the thalamus, and other associated basal regions of the brain are believed to play dominant roles in discrimination of these sensibilities."

"Involvement of the VPL and VPM nuclei of the thalamus, usually because of a vascular lesion, causes loss or diminution of all forms of sensation on the opposite side of the body. Position sense is affected more frequently than any other sensory function."

3. Vascular Anatomy and Etiology

"Occlusion of thalamogeniculate branches arising from the PCA (P2 segment) causes a pure sensory stroke, a sensorimotor stroke, or the thalamic pain syndrome (Dejerine-Roussy syndrome)."

• Thalamic hemorrhage - intracerebral hemorrhage involving the posterolateral thalamus (Harrison's notes patients may develop Dejerine-Roussy syndrome after thalamic hemorrhage)
• Thalamic tumors (gradual onset, unlike the apoplectic onset of stroke)
• MS plaques in thalamus/subthalamic white matter
• Hereditary hemorrhagic telangiectasia (enlarging vascular malformations)

• Apoplectic/sudden = stroke
• Gradual = tumor
• MRI confirms the diagnosis

4. Complete Clinical Features

A. Sensory Deficits (Phase 1 - Acute)

"The common symptoms of thalamic syndrome include pain (thalamic pain), numbness, and hemisensory loss. The pain may be spontaneous or evoked by any form of stimulation. It often has a disagreeable and lasting quality. Patients may also complain of a distorted sense of taste. Right thalamic lesions appear to predominate."

"On examination, a marked hemianesthesia is present which may be dissociated: that is, pain and temperature or light touch and vibration sense may be separately lost. Proprioceptive loss, often with astereognosis, is a common feature. A transitory hemiparesis sometimes occurs."

1. Hemianesthesia (occasional sparing of proprioception)
2. Transient slight hemiparesis
3. Hemiataxia
4. Hemiataxia-hypesthesia syndrome
5. Impaired automatic movements / gait (damaged "automatic pilot")
6. Disequilibrium / "thalamic astasia"
7. Choreoathetoid movements
8. Athetoid posture ("thalamic hand") - characteristic dystonic posture of the hand on the affected side
9. Pain with dysesthesias and allodynia (thalamic pain)
10. Homonymous hemianopia - if medial occipital infarction occurs simultaneously

"Thalamic syndrome: sensory loss (all modalities), spontaneous pain and dysesthesias, choreoathetosis, intention tremor, spasms of hand, mild hemiparesis: Posteroventral nucleus of thalamus; involvement of the adjacent subthalamus body or its afferent tracts."

B. Thalamic Pain (Phase 2 - Subacute to Chronic)

"With partial recovery of sensation or with an acute but incomplete lesion, spontaneous pain, or discomfort (Dejerine-Roussy syndrome; thalamic pain syndrome), sometimes of the most distressing type, may appear on the affected side of the body. A stimulus may then have a diffuse, unpleasant, lingering quality. Thermal - especially cold - stimuli, emotional disturbance, loud sounds, and even certain types of music may aggravate the painful state. In spite of this overresponse to stimuli, the patient usually shows an elevated pain threshold, that is, a stronger stimulus than normal is necessary to produce a sensation of pain (hypalgesia with hyperpathia)."

"An infarct in the thalamus can lead to a loss of sensation. Thalamic pain syndrome can occur during recovery from a thalamic infarct. The syndrome is characterized by chronic pain on the side of the body contralateral to the stroke."

"The severe, persistent, unrelenting unilateral pain often has a burning quality and may be associated with allodynia and hyperpathia. It is persistent and responds poorly to analgesics."

• Location: Usually entire contralateral hemibody; predominantly distal in the limbs
• Quality: Burning, aching, searing, shooting, stabbing, or lancinating
• Timing: Present at rest; exacerbated by any sensory stimulation (allodynia) including touch, temperature changes (especially cold), emotional distress, loud noise, and music
• Onset: Variable - weeks to months to years after the stroke; most frequently within the first 6 months
• Distribution may shift so that it is poorly localized

5. Physiology of Thalamic Pain Generation

"Complete removal of the somatic sensory areas of the cerebral cortex does not prevent pain perception. Therefore, it is likely that pain impulses entering the brain stem reticular formation, the thalamus, and other lower brain centers contribute to conscious perception of pain... the cortex plays an especially important role in interpreting pain quality, even though pain perception might be principally the function of lower centers [i.e., the thalamus]." (Chapter 49 - Role of Reticular Formation, Thalamus, and Cerebral Cortex in Appreciation of Pain)

"Secondary hyperalgesia frequently results from lesions in the spinal cord or the thalamus." (Chapter 49 - Hyperalgesia)

"The pathogenesis of PSP is not yet known. However, it has been suggested that hyperexcitation in the damaged sensory pathways, damage to the central inhibitory pathways, or a combination of the two may be responsible for the onset of PSP."

6. Partial/Variant Forms

"Partial forms (partial geniculothalamic infarct) result from lacunar infarction restricted to one of the penetrating thalamogeniculate vessels and result in pure sensory stroke or sensorimotor stroke. Disease of such small perforating arteries often accompanies diabetes and chronic hypertension."

7. Laterality

8. Associated Nonsensory Features

"Thalamic infarction and hemorrhage are often associated with nonsensory symptoms that can include deficits in memory, executive function, sleep cycle, and other functions."

9. Investigations

• MRI brain (preferred over CT): confirms infarct or hemorrhage in posterolateral thalamus
• MRI DWI: detects acute ischemia within hours
• In delayed presentations: repeat MRI to exclude new pathology (recurrent infarction, hemorrhage, tumor)
• Somatosensory evoked potentials can help confirm thalamic dysfunction

10. Treatment

"Anticonvulsants (carbamazepine or gabapentin) or tricyclic antidepressants may be beneficial."

"Tricyclic antidepressants are still a choice of treatment. Gabapentin and lamotrigine have been used to treat central PSP syndrome in open-labeled studies."

Advanced interventions: "Chronic motor cortex stimulation (MCS) therapy provides pain relief for some poststroke patients. Stereotactic radiosurgery (SRS) of the pituitary and deep brain stimulation (DBS) have been used to treat PSP syndrome with some success."

Summary Table

• Guyton and Hall Textbook of Medical Physiology - Chapters 48 and 49
• Ganong's Review of Medical Physiology, 26th Ed. - Chapter 8
• Adams and Victor's Principles of Neurology, 12th Ed. - Chapter on Hemisensory Loss
• Bradley and Daroff's Neurology in Clinical Practice - Thalamic Syndrome and Poststroke Pain sections
• Harrison's Principles of Internal Medicine, 22nd Ed. - Cerebrovascular disease, Sensory localization
• Localization in Clinical Neurology, 8th Ed. - Syndromes of Thalamic Infarction