What happens to cognitive function following surgery for hypothalamic hamartoma?

Long-term cognitive outcome after radiosurgery in epileptic hypothalamic hamartomas and review of the literature

OBJECTIVE

Epileptic patients with hypothalamic hamartoma (HH) frequently present cognitive impairments. Surgical techniques aiming at HH can be very efficient for epilepsy relief and cognitive improvement but are also demonstrated to carry a significant risk of additional reduction in memory function in these already disabled patients. Gamma knife radiosurgery (GKS) offers an efficient minimally invasive procedure. We evaluated the effect of stereotactic radiosurgery on cognitive outcome.

METHODS

We designed a prospective single-center case series study. Thirty-nine epileptic patients (median age = 17 years, range = 4-50) with HH underwent preoperative and postoperative testing of intelligence quotient (IQ; all patients), including a working memory component, and other memory function testing (for patients ≥16 years old). All patients were prospectively evaluated and underwent complete presurgical and postsurgical clinical, electrophysiological, endocrinal, and visual assessments. In all patients, the postoperative assessment was performed at least 3 years after radiosurgery. We explored what variables correlate with cognitive outcome. Literature review was done for other surgical techniques and their risks for cognitive complications after surgery.

RESULTS

No decline was observed in intellectual ability (including working memory) after GKS, and no memory decline was seen in adults. We observed significant improvement (>1 SD in z-score) in working memory index (46%) and processing speed index (35%), as well as improvement in full-scale IQ (24%), verbal comprehension index (11%), perceptual organization index (21%), verbal learning (20%), and visual learning (33%). Before GKS, the probability of seizure cessation was higher in patients with higher cognitive performance. After GKS, the cognitive improvement was significantly higher in the seizure-free patients compared to the non-seizure-free patients.

SIGNIFICANCE

We found clear cognitive improvement in a high percentage of patients but importantly no significant decline in intellectual ability (including working memory) and no decline in memory in adult patients 3 years after GKS. GKS compares favorably to the other surgical techniques in terms of cognitive outcome, with similar seizure freedom.

Optically pumped magnetometers: From quantum origins to multi-channel magnetoencephalography

Optically Pumped Magnetometers (OPMs) have emerged as a viable and wearable alternative to cryogenic, superconducting MEG systems. This new generation of sensors has the advantage of not requiring cryogenic cooling and as a result can be flexibly placed on any part of the body. The purpose of this review is to provide a neuroscience audience with the theoretical background needed to understand the physical basis for the signal observed by OPMs. Those already familiar with the physics of MRI and NMR should note that OPMs share much of the same theory as the operation of OPMs rely on magnetic resonance. This review establishes the physical basis for the signal equation for OPMs. We re-derive the equations defining the bounds on OPM performance and highlight the important trade-offs between quantities such as bandwidth, sensor size and sensitivity. These equations lead to a direct upper bound on the gain change due to cross-talk for a multi-channel OPM system.

A 3D endoscopic transtubular transcallosal approach to the third ventricle

OBJECT

Surgical approaches to deep-seated brain pathologies, specifically lesions of the third ventricle, have always been a challenge for neurosurgeons. In certain cases, the transcallosal approach remains the most suitable option for targeting lesions of the third ventricle, although retraction of the fornices and wall of the third ventricle have been associated with neuropsychological and hypothalamic deficits. The authors investigated the feasibility of an interhemispheric 3D endoscopic transcallosal approach through a minimally invasive tubular retractor system for the management of third ventricular lesions.

METHODS

Three-dimensional endoscopic transtubular transcallosal approaches were performed on 5 preserved cadaveric heads (10 sides). A parasagittal bur hole was placed using neuronavigation, and a tubular retractor was inserted under direct endoscopic visualization. Following observation of the vascular structures, fenestration of the corpus callosum was performed and the retractor was advanced through the opening. Transforaminal, interforniceal, and transchoroidal modifications were all performed and evaluated by 3 surgeons.

RESULTS

This approach provided enhanced visualization of the third ventricle and more stable retraction of corpus callosum and fornices. Bayonetted instruments were used through the retractor without difficulty, and the retractor applied rigid, constant, and equally distributed pressure on the corpus callosum.

CONCLUSIONS

A transtubular approach to the third ventricle is feasible and facilitates blunt dissection of the corpus callosum that may minimize retraction injury. This technique also provides an added degree of safety by limiting the free range of instrumental movement. The combination of 3D endoscopic visualization with a clear plastic retractor facilitates safe and direct monitoring of the surgical corridor.