Developmental anatomy of thalamus and impact of perinatal lesions

With music as a metaphor for consciousness, the thalamus has been called ‘the conductor’ of the orchestra in the brain, and the network activities of the cerebral cortex as the musicians. Detailed description of the impact of neonatal focal thalamic injury on neurodevelopment is still lacking. This paper aims to understand that relationship better, envisaging neuroprotection based on thalamocortical plasticity, the ability of the brain to reorganize itself by forming new neuronal connections. Neuroprotection refers to therapies used to defend the central nervous system against injury due to neurodegenerative disorders (e.g. trauma, epilepsy, etc.). We gathered information from a search and cross-referencing of the scientific literature, personal observations, and detailed study of neuroimaging.

In newborn infants, the thalamus already contributes to visual, auditory, and pain processing, and to arousal and sleep. Isolated thalamic lesions may present with clinical seizures. Cranial ultrasound can then be used to classify neonatal thalamic injuries. Asphyxia, stroke, infection, and network injury are all common. Experimental work suggests that adaptation to injury, so-called plasticity, in thalamocortical interaction may differ before and after 30 weeks postmenstrual age in newborn infants. It is very likely that plasticity may not provide complete repair given the timing and extent of damage.

The long-term effects of many focal lesions in the thalamus are still unknown. Given early nuclear organization and thalamocortical maturation before 30 weeks postmenstrual age, the effect of even small lesions is most likely underestimated. On the other hand, very little is known about possible adaptive capabilities of the neonatal thalamus. Cranial ultrasound at least offers the ability to locate lesions in the major regions of the thalamus and to compare ultrasound patterns with causal mechanisms.