Thalamic syndrome: symptoms, causes and treatment

The thalamus is a brain structure that serves as a crossroads point for multiple neural pathways (it is a “relay center”). Its lesion causes the thalamic syndrome, a clinical picture that triggers various symptoms, with a predominance of thalamic pain.

Here we will know in detail the causes of this syndrome, as well as its symptoms and possible treatments.

• Related article: "Thalamus: anatomy, structures and functions"

thalamus

The thalamus is a brain structure; is about a central gray core at the base that serves as a crossover point for multiple neural pathways. It is a paired structure, located on both sides of the third ventricle. It occupies approximately 80% of the diencephalon and is divided into four large sections (anterior, medial, lateral and posterior), in turn divided into several nuclei.

All sensitive and sensory pathways that originate in the spinal cord, brainstem and hypothalamus, converge on the thalamus, where they relay (it is a "relay center"). In addition, the different coordination pathways of the extrapyramidal system, vestibular nuclei, cerebellum, striatal nuclei and cerebral cortex are added.

Thalamic syndrome: characteristics

Thalamic syndrome, also known as Déjerine-Roussy Syndrome, is characterized by the following symptoms: transient mild hemiparesis, hemicoreoathetosis, hemihypoesthesia, hyperalgesia, allodynia and hemiataxia with astereognosia of variable intensity. This syndrome occurs with lesions of the posterior nuclei of the thalamus.

The clinical manifestations produced by thalamic lesions are very diverse (since they cover many pathways), little systematizable, relatively infrequent and little known by the clinician, although we can specify them, as we will see later.

This syndrome was first described in early 1903, when Jules Joseph Dejerine and Gustave Roussy were studying the clinical and pathological facts of the thalamic syndrome. His initial description of the thalamic syndrome remains to this day, and few changes have been added to it in the last 100 years. years, although Lhermitte in 1925 and Baudouin in 1930 made important contributions to define the characteristics of hemorrhage thalamic

On the other hand, Fisher emphasized language disorders and ocular motility disorders caused by thalamic lesions.

Thus, on the other hand, twenty years after that first description, Foix, Massson and Hillemand, other researchers, showed that the most common cause of the syndrome was obstruction of the thalamogeniculate arteries (branches of the posterior cerebral artery).

Symptoms

The most distressing symptom of thalamic syndrome is pain; It is a generally intractable, intense, disabling and constant pain. Thalamic pain is of central origin, that is, its origin is found in the cerebral cortex.

The pain, moreover, is refractory and unpleasant, and resists analgesic medication.. Pains usually present as an initial symptom in 26 to 36% of patients. The sensation of pain is burning and stabbing, and is commonly associated with painful hyperesthesia in the same distribution. This hyperesthesia is defined as an exaggerated sensation of tactile stimuli (such as the sensation of tickling).

Other important symptoms in the thalamic syndrome are paresthesias, a transient mild hemiparesis, hemicoreoathetosis, hemihypoesthesia, hyperalgesia, allodynia, and hemiataxia with intensity astereognosis variable.

Specifically, patients with this syndrome manifest a sensory loss contralateral to the lesion in all modalities. In addition, vasomotor disorders, severe dysesthesia of the involved hemibody, and sometimes choreoathetoid or ballistic movements also appear.

Causes

The cause of thalamic syndrome is a lesion in the thalamus. Specifically, this lesion involves the inferior and lateral nuclei.

The most common lesions in thalamic syndrome are of vascular origin (cerebrovascular accidents), although there are also there are lesions of another nature, such as those of metabolic, neoplastic, inflammatory and infectious.

On the other hand, alluding to the vascular origin of the syndrome, thalamic infarcts are generally due to occlusion of one of the four major vascular regions: posterolateral, dorsal, paramedian and anterior.

Treatment

The treatment of thalamic syndrome mainly involves the associated pain. In the past, treatment was based on neurosurgery, with interventions such as thalamotomy (removal of a small area in the thalamus), mesencephalotomies (removal of the midbrain) and cingulotomies (section of the cingulate).

However, new neurosurgical treatments have been established such as spinal cord stimulation, stimulation of the motor cortex and chronic deep brain stimulation, using approximation techniques with stereotaxy.

On the other hand, other new treatments have also been used in recent years, from opioid drugs, tricyclic antidepressants and analgesics-antiepileptics (for example gabapentin).

Bibliographic references:

• Salazar-Zúñiga, A. and Carrasco-Vargas, H. (2006). Treatment of thalamic syndrome (Dejerine-Roussy) secondary to ischemic stroke, with gabapentin. Report of four cases and review of the literature. Neurol Neurocirc Psiquiat, 39(2): 70-75.
• De Betolaza, S., Núñez, M., and Roca, F. (2016). Thalamic lesions: a semiological challenge. Thalamic lesions: a semiological challenge. Uruguayan Journal of Internal Medicine, 1, 12-19.