The thalamus is a brain structure that serves as a crossing point for multiple neuronal pathways (it is a “relay center”). Its injury causes thalamic syndrome a clinical condition that triggers various symptoms, with thalamic pain predominating.
Here we will learn in detail the causes of this syndrome, as well as its symptoms and possible treatments.
The thalamus is a brain structure; is about a central gray nucleus of the base that serves as a crossing point for multiple neuronal 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 the sensitive and sensory pathways that originate in the spinal cord, brainstem and hypothalamus converge in the thalamus, where they take over (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: mild transient hemiparesis, hemicoreoathetosis, hemihypoesthesia, hyperalgesia, allodynia and hemiataxia with astereognosia of variable intensity. This syndrome occurs due to lesions of the posterior nuclei of the thalamus.
The clinical manifestations produced by thalamic lesions are very diverse (since they cover many pathways), not very 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 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, although Lhermitte in 1925 and Baudouin in 1930 made important contributions to defining the characteristics of thalamic hemorrhage.
On the other hand, Fisher emphasized language disorders and alterations in ocular motility produced by thalamic lesions.
Thus, on the other hand, twenty years after that first description, Foix, Massson and Hillemand, other researchers, demonstrated 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 is also refractory and unpleasant, and resists analgesic medication Pain generally occurs as an initial symptom in 26 to 36% of patients. The sensation of pain is burning and lacerating, 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 thalamic syndrome are paresthesias, a mild transient hemiparesis, hemicoreoathetosis, hemihypoesthesia, hyperalgesia, allodynia and hemiataxia with astereognosia of variable intensity.
Specifically, patients with this syndrome manifest a sensory loss contralateral to the lesion in all modalities In addition, vasomotor disorders, severe dysesthesias of the involved hemibody and sometimes choreoathetoid or ballistic movements also appear.
The cause of thalamic syndrome is a lesion in the thalamus. Specifically, This injury involves the inferior and lateral nuclei
The most common lesions of thalamic syndrome are of vascular origin (cerebrovascular accidents), although there are also lesions of another nature, such as those of metabolic, neoplastic, inflammatory and infectious origin.
On the other hand, referring 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
Treatment of thalamic syndrome mainly involves associated pain In the past, treatment was based on neurosurgery, with interventions such as thalamotomies (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, motor cortex stimulation and chronic deep brain stimulation, using stereotactic approach techniques.
On the other hand, other new treatments have also been used in recent years, from opiate medications, tricyclic antidepressants and analgesics-antiepileptics (for example gabapentin).
