Thalamic pain syndrome is a central pain syndrome provoked by damage to the thalamus. The immediate cause of the disease is vascular lesion, which causes infarction of the ventroposteriomedial and ventroposteriolateral thalamic nuclei. Pathology is manifested by severe pain and sensitivity disorders on the side opposite to the affected area in the brain. Diagnosis includes assessment of neurological status, instrumental neuroimaging, and consultation with a psychiatrist. Psychotropic drugs and opioid analgesics are prescribed to relieve thalamic pain, and in refractory cases, a thalamotomy is performed.
ICD 10
G93.8 Other specified brain lesions
General information
Thalamic pain syndrome (Dejerin-Russi syndrome) is a common variant of chronic pain that develops in 8% of patients after acute disorders of cerebral circulation. The clinical picture of the disease was first described in 1906 by French doctors: neurologist J. Dezherin and pathologist G. Russi, who studied the symptoms in patients after a stroke. Pathology is of great importance in practical neurology due to its frequent occurrence, diverse and painful symptoms for the patient, difficulties in selecting an effective pharmacocorrection scheme.
Causes
The main etiological factor of thalamic pain syndrome is ischemic and hemorrhagic strokes. Most cases of the disease are caused by damage to the ventroposteriolateral thalamus. Less often, symptoms occur in the pathology of ventroposteriomedial nuclei. Thrombosis of the thalamo-cranial artery, a branch of the posterior cerebral artery, is recognized as the direct pathomorphological cause of clinical manifestations.
Among the risk factors, hypertension is put in the first place, which causes up to 80% of all hemorrhages in the brain. In the ischemic form of stroke, the main provoking factor is atherosclerosis of cerebral and extracranial vessels. An increased probability of damage to the thalamus and the formation of thalamic pain syndrome is observed in patients with vascular diseases: systemic vasculitis, amyloidosis, arteriovenous malformations. Hemophilia, thrombocytopenia and other blood clotting disorders are an independent risk factor.
Pathogenesis
The thalamus (visual tubercle) is a part of the intermediate brain, which has an ovoid shape and a volume of about 3 cm3. It contains more than 40 nuclei — clusters of neuronal bodies that are separated from each other by layers of white matter. According to localization, the anterior, central, medial, lateral and posterior groups of thalamic nuclei are distinguished. The organ performs sensory, motor and associative functions.
The posterolateral nucleus, which is most often affected by Dejerin-Russi syndrome, is responsible for processing and filtering information from pain, tactile and proprioceptive receptors. Therefore, when neurons are damaged, the incoming information is distorted: tactile signals are perceived as painful, which is the main cause of the development of post-stroke chronic pain and allodynia.
The second component of the thalamic pain syndrome clinic is disorders of the GABAergic neurotransmitter system, which normally inhibits the transmission of pain signals to the somatosensory cortex. The third component of neuropathic pain is central sensitization, which occurs against the background of hyperexcitability of the neurons of the visual hillock, excessive release of glutamate, stable depolarization.
Symptoms
In half of the patients, clinical manifestations occur in the first month after a stroke, 37% of patients experience symptoms in the interval from 30 days to 2 years after a violation of cerebral circulation. In 13% of cases, more than 2 years pass between stroke and the development of thalamic pain syndrome. In such patients, pain and temperature sensitivity changes, the perception of tactile impulses is disrupted.
The main manifestation of the thalamic pain syndrome is severe pain on the side of the body opposite to the lesion. Excruciating sensations are described as stabbing, burning, squeezing and pulsating. Some people compare them to electrical discharges. Chronic pain is constantly exhausting, disrupting performance and daily activity.
Increased pain syndrome is observed during movements, exposure to cold or heat, emotional shocks. However, these same factors can weaken the pain in some patients. In 70% of cases, allodynia develops – painful sensations that occur in response to a non-painful stimulus (warmth, touch). The symptoms are accompanied by contralateral sensitivity disorders and homonymous hemianopia.
Thalamic pain syndrome is characterized by attacks of violent uncontrolled crying or laughter, vegetative-trophic disorders. With extensive damage to the nuclei of the optic tubercle on the opposite side, contracture of the fingers of the hand occurs – the “obstetrician’s hand”. At the same time, the main phalanges are moderately bent, the middle and end phalanges are completely unbent. The fingers of the hand move continuously due to the development of choreoathetosis hyperkinesis.
Complications
Although thalamic pain syndrome does not pose a serious threat to the patient, its symptoms significantly reduce the quality of life. Constant severe pain, which cannot be eliminated with the usual analgesics, cause depressive disorders, neuroses, and carcinophobia. Against the background of particularly painful and prolonged pain attacks, suicidal thoughts may occur.
After a stroke, there are other residual consequences that aggravate the clinical picture of damage to the thalamus. Often there is partial or complete paralysis of certain areas of the body, speech defects, visual and hearing impairments. Despite the development of neurology, full recovery of work activity is possible only in 10% of people who have suffered a stroke. About 85% of patients require constant medical and social support.
Diagnostics
The basis for the diagnosis is a clinical and neurological examination. They take into account information about the stroke, its prescription and the nature of rehabilitation. At the neurologist’s consultation, clinical methods for assessing neuropathic pain are used: a visual analog scale, DN4 and painDETECT questionnaires. As auxiliary diagnostic directions are used:
- CT / MRI of the brain. Modern neuroimaging methods show the presence and degree of damage to the thalamic nuclei, other residual manifestations of stroke, the state of the cerebral cortex and subcortical nuclei.
- EEG. The comprehensive examination program includes an assessment of the functional activity of the brain. According to the results of electroencephalography, foci of increased convulsive readiness are determined, which are typical for strokes, structural and metabolic encephalopathies.
- Consultation of a psychiatrist. If standard examinations do not reveal a connection between an organic lesion of the thalamus and pain syndrome, it is necessary to exclude psychogenic variants of pain. Diagnosis includes a clinical conversation with a doctor, testing and filling out questionnaires.
Signs of thalamic pain syndrome must be distinguished from other variants of neuropathic pain. Differential diagnosis is carried out with multiple sclerosis, compression neuropathies, postherpetic neuralgia. During the extended examination, diabetic neuropathy, HIV-related neuralgia, pain caused by trauma or degenerative diseases of the spinal cord are excluded.
Treatment
Conservative therapy
To eliminate chronic pain, pathogenetic therapy is necessary, which affects the mechanisms of the appearance of symptoms and increases the activity of its own antinociceptive system. The effectiveness of tricyclic antidepressants, which in medium-high doses reduce burning and excruciating pain, stop the manifestations of allodynia, has been most studied. The use of amitriptyline gives a stable clinical effect in 66% of patients.
Experts of the European Federation of Neurological Communities recommend pregabalin as a first-line drug for thalamic pain syndrome. The use of other types of anticonvulsants is being considered, but their effectiveness in post-stroke pain has not been clinically proven. With insufficient effect from psychotropic drugs, opioid analgesics are indicated, which are used under strict medical supervision to prevent addiction.
NMDA receptor antagonists are used as experimental therapy, which affect the mechanisms of pain memory and prevent the chronization of thalamic pain. In complex treatment, cognitive behavioral psychotherapy is used, which helps people cope with unpleasant symptoms, prevents the development of post-stroke depression. In rare cases, transcranial magnetic stimulation is resorted to.
Surgical treatment
In the absence of the effect of conservative tactics and the preservation of excruciating pains that interfere with a full life, the indications for thalamotomy are evaluated. During the operation, stereotactic destruction of the thalamic nuclei is performed, after which the pain syndrome decreases. In neurosurgery, such an intervention is rarely performed and only in difficult cases, since there are risks of irreversible side effects after surgery.
Prognosis and prevention
Medication and other methods of treating thalamic pain have limited effectiveness, so the prognosis is doubtful. Prevention of Dejerin-Russi syndrome is to prevent its cause – disorders of cerebral blood flow. It is necessary to regularly monitor blood pressure, timely and combined therapy of hypertension, correction of blood lipid composition by diet therapy and pharmacotherapy.