Takatsugu Shimazaki

Peripheral nervous system in the larynx: an anatomical study of the motor, sensory and autonomic nerve fibers

The laryngeal peripheral nervous system is presented on the basis of our results in the cat, following 10 years of investigation using mainly tracer techniques. The present paper focused on the localization of each laryngeal motoneuron, the myotopical arrangements of motoneurons innervating the pharyngeal and esophageal striated muscles within the nucleus ambiguus in the motor nerve supply, and also on the location of neurons, the distribution and density of nerve fibers, the area and laterality of the innervation, and the pathway to the larynx in the sensory and sympathetic nerve supplies. Regarding the parasympathetic nerve supply, the neural ganglia and the ganglionic cells in and around the laryngeal nerves and in the laryngeal framework are demonstrated. Most of this innervation, however, is still unclear. Discussions from the literature are also reported.

Ganglions and Ganglionic Neurons in the Cat's Larynx

Localization, projections and role of ganglia and ganglionic neurons in the laryngeal framework were demonstrated in cats. Six to 8 large size ganglia containing 50 to 80 ganglionic neurons per ganglion in the paraglottic space, 4 to 6 small ganglia involving 5 to 25 cells in each ganglion dorsal to the posterior cricoarytenoid muscle, and 1 to 3 small ganglia including 15 to 25 perikarya per ganglion around the inferior laryngeal nerve were observed. Each ganglion showed spindle shaped covering fibrous capsule. Ganglionic neurons totaling 600 to 800 were oval shaped with an average diameter of 25 microns. Projections of the ganglionic neurons to the superior cervical ganglion (SCG) and nodose ganglion (NG) through the ipsilateral internal branch of the superior laryngeal nerve and to periphery were detected. From the dorsal motor nucleus of vagus, SCG and NG, the ganglionic cells received projections ipsilaterally. On immunocytochemistry many vasoactive intestinal polypeptide (VIP)-immunoreactive (ir) neurons, some neuropeptide Y (NPY)- and tyrosine hydroxylase (TH)-ir neurons and a few substance P (SP)-ir cells were recognized in ganglions. VIP-, NPY-, TH-, SP-, and calcitonin gene-related peptide (CGRP)-ir fibers were also observed in and around vessels and glands. Following denervation, VIP-, NPY- and TH-ir neurons and fibers did not change. These results prove that laryngeal ganglionic neurons have endogenic autonomic, especially cholinergic nature and innervate vessels and glands.

Laryngeal solitary multiple mucosal neuromas without multiple endocrine neoplasia (MEN) type 2B

The first case of laryngeal solitary multiple mucosal neuromas (MMN) was reported. A 73-year-old man who had complained of hoarseness and abnormal prickly sensation in the throat for 3 months visited our hospital. Many small whitish-yellow nodules were observed in the laryngeal mucosa from the right arytenoid to the interarytenoid region. Using laryngomicroscopy biopsy was performed twice. The pathological study showed neurogenic nodular lesions consisting of regularly arranged nerve bundles with many axons and Schwann cell proliferation, and so MMN was finally diagnosed. As MMN is regarded as a constant component of multiple endocrine neoplasia (MEN) type 2B, screening of MEN type 2B was performed, however, they were all within normal limits. This case was, therefore, diagnosed as a laryngeal solitary MMN without MEN type 2B.

Two cases of piriform sinus fistula which required a long time for diagnosis

Two cases of piriform sinus fistula which had contradistinctive occurrences, were reported. In case 1, a 58-year-old man suffered from the disease without having any symptom for a long time and in case 2, a 39-year-old woman had been troubled with repeated cervical abscess from 3 years old. In both cases, indirect laryngoscopy and laryngofiberscopy showed saliva pooling in the bilateral piriform sinus and barium fluoroscopy with the Valsalva maneuver revealed the fistula originating from the apex of left piriform sinus. In case 2, computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated an abscess in and around the left lobe of the thyroid. In both cases the fistulectomy was performed and their postoperative conditions have been uneventful for more than 2 years without recurrence. The etiology, cause, clinical features, diagnosis and therapy of piriform sinus fistula were reviewed.

Morphological Study of the Intrapharyngeal Ganglia and Ganglionic Neurons in Cats

The distribution, number and nature of intrapharyngeal ganglia and their neurons in cats were examined by means of serial sections, histochemical and immunohistochemical methods. Six to eight large ganglia around the palatine tonsils and five to eight small ganglia in the laterodorsal wall of pharyngeal mucous membrane were observed. The intrapharyngeal ganglionic neuron (25-30 microns in diameter) totalled 600-800 and more than 80% of them were located around the palatine tonsils. The ganglionic neurons were acetylcholinesterase reaction positive. On immunohistochemistry, many choline acetyltransferase-immunoreactive and vasoactive intestinal polypeptide-immunoreactive neurons and a few tyrosine hydroxylase-immunoreactive nerve cells were found, but no calcitonin gene-related peptide-immunoreactive or substance P-immunoreactive neurons were recognized in the ganglion. The present findings indicate that intrapharyngeal ganglionic neurons are mainly parasympathetic and partially sympathetic in nature.

Arrangement and number of intralaryngeal ganglia and ganglionic neurons: comparative study of five species of mammals

The arrangement and number of intralaryngeal ganglia and their neurons in five mammals (dog, rat, guinea pig, rabbit and cat) were examined morphologically. Intralaryngeal ganglions were situated mainly in branches of the internal branch of superior laryngeal nerve (Int-SLN), dorsal and/or dorsolateral to the posterior cricoarytenoid muscle, and around the inferior laryngeal nerve in dogs, rats, guinea pigs and cats, but they were identified at the branching out point of the Int-SLN exclusively in rabbits. The ganglion of each animal was spindle-shaped, with a surrounding fibrous capsule, and it contained many ganglionic neurons, vessels and connective tissue cells. The ganglionic neuron was oval-shaped and had a round nucleus: the diameter was smaller (20-25 microns) in the rat than in the other mammals (25-30 microns). More than 80 per cent of ganglionic neurons occurred in the supraglottis of all the animals except the rat. In the rat, this value was approximately 40 per cent.