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Carlo Serra, Lelio Guida, Victor E. Staartjes, Niklaus Krayenbühl and Uğur Türe

The authors report on and discuss the historical evolution of the 3 intellectual and scientific domains essential for the current understanding of the function of the human thalamus: 1) the identification of the thalamus as a distinct anatomical and functional entity, 2) the subdivision of thalamic gray matter into functionally homogeneous units (the thalamic nuclei) and relative disputes about nuclei nomenclature, and 3) experimental physiology and its limitations.

Galen was allegedly the first to identify the thalamus. The etymology of the term remains unknown although it is hypothesized that Galen may have wanted to recall the thalamus of Odysseus. Burdach was the first to clearly and systematically define the thalamus and its macroscopic anatomy, which paved the way to understanding its internal microarchitecture. This structure in turn was studied in both nonhuman primates (Friedemann) and humans (Vogt and Vogt), leading to several discrepancies in the findings because of interspecies differences. As a consequence, two main nomenclatures developed, generating sometimes inconsistent (or nonreproducible) anatomo-functional correlations. Recently, considerable effort has been aimed at producing a unified nomenclature, based mainly on functional data, which is indispensable for future developments. The development of knowledge about macro- and microscopic anatomy has allowed a shift from the first galenic speculations about thalamic function (the “thalamus opticorum nervorum”) to more detailed insights into the sensory and motor function of the thalamus in the 19th and 20th centuries. This progress is mostly the result of lesion and tracing studies. Direct evidence of the in vivo function of the human thalamus, however, originates from awake stereotactic procedures only.

Our current knowledge about the function of the human thalamus is the result of a long process that occurred over several centuries and has been inextricably intermingled with the increasing accumulation of data about thalamic macro- and microscopic anatomy. Although the thalamic anatomy can currently be considered well understood, further studies are still needed to gain a deeper insight into the function of the human thalamus in vivo.

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Lelio Guida, Kevin Beccaria, Sandro Benichi, Anaïs Chivet, Timothée de Saint Denis, Syril James, Giovanna Paternoster, Michel Zerah, Stéphanie Puget and Thomas Blauwblomme

OBJECTIVE

Pediatric patients with long-term shunts may experience specific complications related to the segregation of the supra- and infratentorial spaces along with different pressure regimens, leading to either mesencephalic syndromes during shunt dysfunction or isolated fourth ventricle (IFV). An accepted treatment to reestablish normal CSF pathways and reequilibrate the transtentorial pressures is endoscopic aqueductal stenting (EAS) to avoid restenosis. In the present paper, the authors studied children treated with EAS during the last decade for both IFV and obstructive hydrocephalus, evaluated its impact on the course of the disease, and identified prognostic factors for EAS success.

METHODS

A noninterventional retrospective study of routinely acquired data was performed, including all hydrocephalic children undergoing EAS between 2011 and 2019 at Hôpital Necker, Paris, France. The following variables were analyzed: etiology of hydrocephalus; number of surgeries before and after stent placement; indication for EAS; type of stent connection (i.e., connected or not to a ventriculoperitoneal shunt); and the stent position. Stent failure was defined as the need to perform further shunt revision. Univariate and multivariate analyses were run to identify factors associated with stent failure.

RESULTS

Seventeen patients with a mean age at stent placement of 6 years (SD 6.5 years, range 1 month–18 years) and with a mean follow-up after EAS of 47.5 months (SD 33.7 months, range 5–120 months) were included in the analysis. The etiology of hydrocephalus was as follows: obstructive tumoral (41%), posthemorrhagic (35%), postinfectious (12%), and dysraphism related (12%). The indication for EAS was IFV (47%), rostral midbrain dysfunction syndrome (35%), prevention of secondary aqueductal stenosis after debulking surgery (12%), or primary aqueductal stenosis (6%). No transient or permanent neurological deficits related to the procedure were observed. After EAS, 10 patients did not require further surgeries (59%), and for the others the number of hydrocephalus-related surgeries significantly decreased after stenting. In univariate analysis posthemorrhagic etiology and prevention of aqueductal stenosis were identified as predictors of a good outcome, whereas in multivariate analysis posthemorrhagic hydrocephalus was found to predict a favorable outcome.

CONCLUSIONS

The results confirm EAS as a first-line treatment for IFV and suggest its efficacy in changing the history of hydrocephalic patients who have undergone multiple operations and who experience rostral midbrain dysfunction syndrome, as well as efficacy in the prevention of aqueductal stenosis in selected cases of obstructive tumoral hydrocephalus.