NADPH-diaphorase-positive neurons in the human inferior colliculus: morphology, distribution and clinical implications.

Using the nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) reaction with nitroblue tetrazolium, we provided a detailed investigation of the distribution, dimensional characteristics and morphology of NADPH-d-positive neurons in the three main subdivisions of the human inferior colliculus (IC): central nucleus, pericentral nucleus, and external nucleus. In accordance with their perikaryal diameter, dendritic and axonal morphology, these neurons were categorized as large (averaging up to 45 µm in diameter), medium (20-30 µm), small (13-16 µm) and very small (7-10 µm). Their morphological differences could contribute to varying functionality and processing capacity. Our results support the hypothesis that large and medium NADPH-d-positive cells represent projection neurons, while the small cells correspond to interneurons. Heretofore, the very small NADPH-d-positive neurons have not been described in any species. Their functions-and if they are, indeed, the smallest neurons in the IC of humans-remain to be clarified. Owing to their location, we posit that they are interneurons that connect the large NADPH-d-positive neurons and thereby serve as an anatomical substrate for information exchange and processing before feeding forward to higher brain centers. Our results also suggest that the broad distribution of nitric oxide (NO) synthesis in the human IC is closely tied to the neuromodulatory action of NO on collicular neurotransmitters such as GABA and glutamate, and to calcium-binding proteins such as parvalbumin. A deeper understanding of the relationship between NADPH-d-positive fibers in all IC connections and their co-localization with other neurotransmitters and calcium-binding proteins will assist in better defining the function of NO in the context of its interplay with the cerebral cortex, the sequelae of the aging process and neurodegenerative disorders.

[Bronchopleural fistula after transbronchial passage of a feeding tube]. / Fistule bronchopleurale après passage transbronchique d'une sonde d'alimentation.

Inadvertent transbronchial insertion of a narrow-bore feeding tube using a metallic wire resulted, twice in less than 24 hours, in a right pneumothorax complicated by a bronchopleural fistula. This accident occurred in a conscious patient but with central neurologic chronic disorders recently aggravated by a postoperative Gayet-Wernicke syndrome. The incidence of transbronchial insertion is relatively important [2 to 4%]. Risk factors include a previous endotracheal intubation and an altered mental status. The insertion may be especially hazardous when the patient is uncooperative or unconscious or has lost the cough reflex. The presence of a cuffed endotracheal tube should not be considered as a safeguard for tracheobronchial penetration. Recommendations for prevention are presented. The usual procedure of testing for proper location of the tube following its insertion consisting in the injection of air through the tube with auscultation for gastric borborygmi, is inadequate and should no longer be used.