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The autonomic nerves of the cat middle ear mucosa were studied by the methods of surface preparation, histochemistry and electron microscopy. The tympanic nerve was found to contain large myelinated fibers probably of a sensory nature. Other sympathetic bundles consisted primarily of unmyelinated fibers with a sparse distribution of myelinated fibers. The inferior tympanic artery was accompanied by many vasomotor nerves and its branches were also innervated predominantly by adrenergic fibers. A dense neural network which showed acetylcholinesterase activity was found in the mucosa around the Eustachian tube orifice. These nerves consisted of several unmyelinated fibers encapsulated by a single Schwann cell just below the epithelium. The fine structure of the small ganglions of the tympanic plexus revealed that the cholinergic nerve endings synapse with the cell body of the ganglion. This finding suggests that these ganglions are autonomic.

It is well known that diphenylhydantoine (DPH) can cause such side effects as gingivitis, hypertrichosis, ataxia, nystagmus, diplopia and others. Although there are many reports about DPH intoxication, very few papers mention the neurotological aspects of this condition. Three cases of DPH intoxication which manifested neurotological changes were treated. The common remarkable findings of these cases were equilibrium disturbance, gaze nystagmus and the absence and/or irregularity of optokinetic nystagmus (OKN). As other neurotological findings do not show any peripheral labyrinthine lesion, the equilibrium disturbances noticed in our cases probably did not originate from the labyrinth but from the central nervous system (CNS). The precise origin of gaze nystagmus noted in these cases has not yet been clarified. It seems to be evident, however, that this type of gaze nystagmus is not due to a peripheral labyrinthine lesion. It is well known that the inhibition or the disturbance of OKN may be caused by central lesions, but the origin or localization of the dysfunction in the CNS has not yet been clarified. On the other hand, animal experiments and postmortem examination of patients with DPH intoxication reveal that the main histologic lesions are located in the cerebellum, especially in the Purkinje cells. Although the precise localization of the lesions in our cases is not known the relationship between clinical findings and histological findings of DPH intoxication can be emphasized.