Thalamic Syndromes and Central Post-Stroke Pain
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Direct answer
Thalamic syndromes are stroke syndromes of the thalamus, and the posterior thalamic territory supplied by the thalamogeniculate branch of the posterior cerebral artery produces Dejerine-Roussy syndrome. It causes contralateral hemisensory loss, dysaesthesia and, in many patients, central post-stroke pain that appears weeks to months after the event. Treatment relies on neuropathic agents such as amitriptyline and gabapentinoids, since responses are often only partial.
What you must remember
- Thalamogeniculate artery: a branch of the posterior cerebral artery that supplies the ventral posterolateral nucleus, and whose occlusion causes the classic Dejerine-Roussy picture.
- Dejerine-Roussy syndrome: contralateral hemianaesthesia, transient hemiparesis, hemiataxia and a painful dysaesthetic hemibody.
- Paramedian thalamic syndrome: bilateral lesions from the basilar tip cause somnolence, memory impairment, behavioural change and vertical gaze abnormalities.
- Central post-stroke pain: burning, cold or electric-shock-like pain in the contralateral body, with a latency of weeks to months after the stroke.
- Allodynia and hyperpathia: light touch, cold and movement provoke disproportionate pain, reflecting loss of spinothalamic inhibition.
- First-line drugs: amitriptyline, gabapentin and pregabalin are commonly used, while lamotrigine and tramadol are second-line options.
- Neuromodulation: motor cortex stimulation is reserved for refractory cases in specialist centres.
- Mimics: shoulder pain, complex regional pain syndrome and spasticity-related pain are common after stroke and must be excluded.
A stepwise approach to a thalamic stroke with pain
Thalamic stroke patients are assessed for the territory first and the pain second, because the lesion pattern guides prognosis and the pain is often delayed.
- Localise the territory: test contralateral sensation, including joint position and vibration, and check gaze, alertness and memory to separate posterolateral from paramedian territories.
- Image the lesion: MRI with diffusion-weighted imaging shows the infarct more clearly than a plain CT, which can be normal early.
- Ask about pain: enquire about burning, cold or allodynia in the affected hemibody, remembering that onset is often delayed.
- Exclude mimics: check for shoulder pain, complex regional pain syndrome and spasticity-related pain before attributing pain to the thalamus.
- Start a neuropathic agent: amitriptyline or a gabapentinoid, titrated to effect, with caution in older patients and those with cardiac disease.
- Add or switch: lamotrigine or tramadol may be used when first-line drugs fail or are not tolerated, with long-term opioids avoided.
- Refer for neuromodulation: motor cortex or thalamic stimulation is considered only for refractory pain under specialist care.
Where the exam tries to catch you
Thalamic questions turn on which territory is involved and which drug is actually supported.
- Trap: placing Dejerine-Roussy syndrome in the anterior thalamus Correct: the syndrome reflects posterior thalamic involvement through the thalamogeniculate artery.
- Trap: expecting pure sensory loss from a paramedian infarct Correct: bilateral paramedian lesions cause somnolence, memory impairment and gaze abnormalities instead.
- Trap: choosing carbamazepine as first-line for thalamic pain Correct: carbamazepine is the drug of trigeminal neuralgia, and its evidence in central pain is weak.
- Trap: treating delayed contralateral pain as a new stroke Correct: central post-stroke pain often begins weeks to months later, so imaging is needed only if new deficits appear.
Frequently asked questions
What causes Dejerine-Roussy syndrome?
Dejerine-Roussy syndrome is caused by infarction of the posterior thalamus, most often through occlusion of the thalamogeniculate branch of the posterior cerebral artery. It produces contralateral hemisensory loss, dysaesthesia and delayed central pain.
When does central post-stroke pain typically begin?
Central post-stroke pain typically begins weeks to months after the causative stroke rather than immediately. It affects the body contralateral to the lesion and is usually described as burning, cold or dysaesthetic.
Which drugs are used first line for central post-stroke pain?
Amitriptyline, gabapentin and pregabalin are commonly used first line for central post-stroke pain, although response is often partial. Lamotrigine and tramadol are second-line options when first-line drugs fail or are not tolerated.
What is the arterial supply of the thalamus?
The thalamus is supplied mainly by the posterior circulation, with the posterior cerebral artery giving thalamogeniculate and posterior choroidal branches. Paramedian thalamoperforating arteries arise near the basilar tip, and occlusion of each territory produces a distinct thalamic syndrome.
Why does a thalamic stroke cause contralateral hemianaesthesia?
A thalamic stroke causes contralateral hemianaesthesia because the ventral posterolateral nucleus relays medial lemniscal and spinothalamic input to the somatosensory cortex. Loss of this relay produces sensory loss on the opposite side of the body.