The Primary Study Of The Perilymph Drainage To Cervical Lymph Nodes In Guinea Pigs

Objective:To ascertain the connection between the perilymph and the cervical lymphatic system in guinea pig,and to explore the perilymph's drainage pathways to the cervical lymph nodes.Methods:23 healthy adult guinea pigs were randomly divided into 3 groups: perilymph group(group A,n=10),middle ear group with the mucosa scraped(group B,n=10) and middle ear group with the mucosa not scraped(group C,n=3).Group A and group B were randomly divided into 2 subgroups:group A1(n=7) and group A2 (n=3);group B1(n=7) and group B2(n=3).For the guinea pigs of group A,the nanocarbon(NC) suspension was injected into the perilymph in their left scala tympani through the round window membrane;for the animals of group B,the tracer was injected into their left middle ear cavity after the mucosa scraped;for the animals of group C,the tracer was injected into their left middle ear cavity without the mucosa scraped.The right side were not injected and served as a control.24 hours after the injection of the tracer,the animals of group A1,group B1 and group C were killed by intracardiac perfusion with normal saline;and 48 hour after the injection of tracer,the animals of the group A2 and group B2 were killed.The four groups of cervical lymph nodes(mandibular,parotid,superficial ventral cervical,and deep cranial cervical lymph nodes) were dissected and collected.The cranium was removed and the intracalvarium tissues and structures were carefully observed.Acoustic vesicles of both sides were collected and opened to observe whether the middle ear cavity mucosa,cochlea and vestibule were stained.The cervical lymph nodes and decalcifying inner ear were made into frozen section and then under H-E staining.The slices were observed with the microscope to find out the stained places and the stained degree.Results:The left parotid lymph nodes and bilateral deep cranial cervical lymph nodes in the animals of group A were black stained;in the animals of group B,only the left parotid lymph nodes and left deep cranial cervical lymph nodes were slightly black stained;in the animals of group C,none of the cervical lymph nodes was stained.The nanocarbon particles was seen in the perilymph of scala tympani and scala vestibuli, the periosteum of scala tympani and scala vestibuli,spiral ligament,space around spiral ganglion and spiral vein of modiolus,the membrane of sacculus proprius and alveus communis after it was injected in the perilymph of the scala tympani,and the endolymphatic sac was also obviously stained,but there was no nanocarbon particles in the endolymph either in the cochlea or in the vestibule.There was no nanocarbon particles either in the inner ears of the animals of group B or of group C.In the animals of group A,the bilateral arachnoid around the cerebellomedullary cistern and part of the cerebral pia mater of myelencephalon were stained black,and their left endolymphatic lacs were obviously black,and their bilateral basicranial external coat of vessels and epineurium of cranial nerves were also slightly black.The animals of group B and group C had no encranial structures stained.Conclusions:There are connections between the perilymph and the cervical lymph nodes in guinea pigs.There might be two drainage pathways:one is that the tracer in the perilymph diffuses to the endolymphatic sac through the connective tissue space surrounding the endolymphatic duct,and enters into the lymphatic capillaries around endolymphatic sac and was eventually drained into the ipsilateral parotid lymph node and deep cranial cervical lymph node;the other is that the perilymph could enter into the cerebral spinal fluid(CSF) through the space around spiral vein of modiolus and spiral ganglions,and then it enters into the lymphatic capillary around cervical external coat of vessels and epineurium through basicranial external coat of vessels and epineurium of cranial nerves,and finally drained to bilateral deep cranial cervical lymph nodes.