Anatomic and surgical approach to the ethmoidal nerve and parasympathetic innervation of the nasal and cerebral circulation in sheep

Objective-To describe an anatomic and surgical approach to the efferent par asympathetic branches of the pterygopalatine ganglia in sheep, with particu lar reference to the ethmoidal nerve and innervation of nasal and cerebral blood vessels. Animals-12 adult sheep used for monolateral (n = 7) or bilateral (n = 5) et hmoidal neurectomy; 2 sheep used for angiography (1 live sheep for digital subtraction angiography, 1 embalmed cadaver for injection studies); and 5 e mbalmed cadavers, 4 frozen specimens, and 2 dry skulls used for dissection, x-rays, and computed tomographic (CT) or magnetic resonance (MR) scans. Procedure-Transverse (coronal) MR scans, transverse, sagittal, and dorsal C T scans, radiography, angiography, photographic images, and dissections of embalmed material were used to study the topographic anatomy of the tempora l and pterygopalatine fossae of the head. Results-images were stored, then compared with photographs of frozen sectio ns from the same or a similar specimen to plan a surgical approach to the e thmoidal nerve. Mono- and bilateral experimental ethmoidal neurectomies wer e performed, allowing characterization of a safe and reliable method. The s eries of pterygopalatine ganglia typical of this species was localized, dis sected, and analyzed for topographic relations. Conclusions-From the result s, a new approach to the efferent branches of the pterygopalatine ganglia ( ethmoidal nerve) for experimental parasympathectomy of the cerebral and nas al circle is proposed. This experimental approach could be used for studies involving thermoregulation of the face, and in experimental control of blo od flow in the nasal cavity and rostral part of the brain.