BACKGROUND. The nucleus accumbens (NAc) has been a target for deep brain stimulation (DBS) in the treatment of depression and obsessive-compulsive disor

To describe the rare finding of a double massa intermedia (MI). Typically, the MI (interthalamic adhesion) is a single bridge of gray matter connecting the medial surfaces of the thalami. Twelve formalin- and alcohol-fixed human third ventricles were examined from superior to inferior by fiber dissection technique under ×6 to ×40 magnifications and with the endoscope. In all hemispheres, the anterior and posterior commissure were defined. The MI, which bridges the medial surfaces of the thalami, was defined in all hemispheres. In one hemisphere, there was a second bridge between the thalami, located posteroinferior to the common MI. Endoscopic view confirmed that there was a second MI in this specimen. The MI usually traverses the third ventricle posterior to the foramen of Monro and connects the paired thalami. The MI is an important landmark during endoscopic and microscopic surgeries of the third ventricle. Although a double MI is very rare, surgeons should be aware of the possibility in their surgical planning. The surgeon should be aware of the possibility of a double MI to avoid confusion during third ventricle surgery.

Background and Objectives: The optimal surgical technique for Chiari type I malformation (CM-I) remains debated, particularly in patients without syringomyelia. While duraplasty (DP+) may enhance radiological outcomes, it can carry higher complication risks. We compared clinical, radiological, and morphometric outcomes after suboccipital decompression with DP+ and without duraplasty (DP−), with prespecified subgroup analyses by syringomyelia status. Materials and Methods: Ninety-three consecutive adult CM-I underwent DP− (n = 54) or DP+ (n = 39) between 2014 and 2022. Pre- and post-operative MRI and neurological evaluations were obtained at 1 year. Functional recovery was assessed using the Chicago Chiari Outcome Scale (CCOS). Clinical and radiological outcomes, complication rates, and subgroup results (with vs. without syringomyelia) were compared. Results: Overall clinical improvement was observed in 92.5% of patients (DP−: 94.4%; DP+: 89.7%; p > 0.05). Among patients without syringomyelia, clinical improvement remained high with DP−. Radiological benefit—including syrinx regression and mega cisterna magna formation—was greater with DP+ (64.1% vs. 24.1%; p < 0.001), but this did not translate into improved functional outcomes (p > 0.05). Cerebellar slump occurred more often after DP+ (30.8% vs. 9.3%; p < 0.05). Complication rates, particularly CSF-related events, were significantly higher with DP+ (17.9% vs. 3.7%, p = 0.032). Morphometric expansion of the foramen magnum did not correlate with functional outcomes. Conclusions: At 1-year follow-up, suboccipital decompression without duraplasty appears to provide comparable clinical improvement to DP+, with fewer complications, in selected CM-I patients without syringomyelia. Duraplasty offers radiological advantages, especially for syringomyelia, but at the cost of increased risk. Longer follow-up is necessary to determine the durability of these findings.