The structural organization and fine distribution of the lymphatic networks in the periodontal tissues (gingiva, periodontal membrane, and alveolar process) and dental pulp of animals and humans were reviewed with special reference to histochemical examination by light and electron microscopy. The distinction between lymphatics and blood vessels was made on cryostat sections of undecalcified and calcified teeth treated with EDTA solution and whole mount preparations of periodontal membranes using 5'-nucleotidase (5'-Nase)-alkaline phosphatase (ALPase) double staining. This staining procedure allowed lymphatic vessels in the periodontal tissue and dental pulp to be differentiated from blood vessels. The specificity and localization of the enzyme reactions were confirmed by comparative histochemical studies of the same specimen with light microscopy and scanning or transmission electron microscopy. Well-developed 5'-Nase-positive lymphatic networks were observed on the tissue sections and whole mount preparations of the gingiva, periodontium, and dental pulp. More lymphatic vessels were seen in the root area of the periodontium than in the cervical area. In the dental pulp, lymphatic vessels were more numerous in the central part than in the peripheral odontoblastic layer. These distributions of the lymphatic capillary networks are discussed in relation to their ability to supply lymph to the teeth.

The existence of lymphatic vessels in the human dental pulp and their distribution were established by light and electron microscopy using an enzyme-histochemical method. The distinction between lymphatic and blood vessels was made by light microscopy on cryostat sections of undecalcified and decalcified teeth using 5'-nucleotidase(5'-Nase)-alkaline phosphatase double staining. On the tissue surface, 5'-Nase-positive lymphatic vessels were highlighted with good contrast and resolution by backscattered electron imaging using scanning electron microscopy. By transmission electron microscopy, dense granular precipitations resulting from the 5'-Nase reaction were seen on the luminal surface of the lymphatic endothelial cells as well as in the area at the basal side, but were absent in the blood vessels. These lymphatic vessels were more numerous in the central part than in the peripheral odontoblastic layer.

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要旨： MRI 3Key words: supranuclear facial nerve palsy, supranuclear hypoglossal nerve palsy, medial medullary infarction, MRI, corticobulbar tract A 65 year-old man was admitted to our hospital due to sudden onset of left hemiparesis and dysarthria. In addition, he presented with left supranuclear facial nerve palsy and deep sensory disturbance in the left trunk and extremities. He showed deviation of the tongue to the left side on protrusion. Because fasciculation and atrophy of the tongue was undetectable three weeks after the onset, his hypoglossal nerve palsy was presumed to be supranuclear in origin. MRI revealed an infarction involving the ventromedial portion of the right upper and middle medulla oblongata extending to the tegmentum. We considered that the contralesional supranuclear facial and hypoglossal nerve palsy in this patient was caused by the disruption of supranuclear fibers projecting onto the contralesional facial and hypoglossal nerve nuclei before their decussations in the upper to middle medulla oblongata. This patient suggested that variant decussations of supranuclear facial and hypoglossal fibers may exist on any levels of the medulla oblongata.