Parasympathetic Nucleus of Facial Nerve

Neurology of Lacrimation

Michael Davidson Professor, Ophthalmology Diplomate, American College of Veterinary Ophthalmologists

Department of Clinical Sciences College of Veterinary Medicine North Carolina State University Raleigh, North Carolina, USA Trigeminal Nerve and Lacrimation

 Sensory afferent from lacrimal gland, adnexa, eye – through ophthalmic division and first branch of maxillary division

(zygomatic n.) maxillary branch  To trigeminal ganglion ophthalmic branch – adjacent to petrous temporal bone lateral to mandibular branch cavernous sinus near middle ear trigeminal ganglion  Terminal branches of trigeminal n. trigeminal nerve distributes sympathetic and parasympathetic efferent to lacrimal gland and face Trigeminal-Lacrimal Reflex

 Afferent arm = CN V, ophthalmic division ⇒trigeminal ganglion ⇒ principle CN V nuclei

 Efferent arm = parasympathetic efferent to lacrimal gland(s)

 Elicits reflex tearing

 Parasympathetic efferent also supplies basal stimuli for lacrimation www.slideplayer.com Parasympathetic Efferent to Lacrimal Gland

 CN VII parasympathetic nuclei  ⇒ greater petrosal nerve (petrous temporal bone)  ⇒ nerve of pterygoid canal (with post ganglionic sympathetics)  ⇒ synapse in pterygopalatine ganglion (ventral periorbital region, near apex of orbit)  ⇒ zygomatic nerve (CN V, maxillary division)*  ⇒ zygomaticotemporal nerve  ⇒ acinar cells of lacrimal gland**

*some texts state postganglionic parasympathetic fibers also in lacrimal nerve (ophthalmic division CNV) **postganglionic parasympathetic innervation to nictitans gland undefined but presumably through zygomatic and infraorbital nn. which carry sympathetics to nictitans www.studyblue.com Zygomatic n.

Caudal nasal nerve Parasympathetic nuclei of CN VII Greater petrosal nerve and n. of pterygoid canal Efferent Arm of Lacrimation

Lacrimal gland Zygomaticotemporal n. Branches to periorbita

N. of pterygoid canal

Caudal nasal n.

Pterygopalantine ganglion Efferent Arm of Lacrimation and Nasal Secretion

 CN VII parasympathetic nuclei ⇒ major petrosal nerve ⇒ nerve of pterygoid canal (with sympathetic fibers) ⇒ synapse on pterygopalatine ganglion ⇒ caudal nasal nerve (maxillary division of CNV) to lateral nasal gland Neurogenic KCS

 lesions along efferent arm of lacrimation pathway: – parasympathetic nucleus of facial nerve – main trunk of facial nerve – near geniculate ganglion – major petrosal nerve – nerve of the pterygoid canal – pterygopalatine ganglion – postganglionic parasympathetic fibers  xeromycteria (dry nasal mucosa) common finding Neurogenic KCS: Lesions in Petrous Temporal Bone

 Most commonly from otitis: – KCS – xeromyceteria Neurogenic KCS: Lesions in Petrous Temporal Bone  May have concurrent: – neurotropic keratitis (CNV) Major petrosal n. Trigeminal n. – anesthesia to Abducen n. eyelids (CNV) Geniculate ganglion – Horner syndrome Facial n. Vestibular n. – facial n. paralysis Cochlear n. (CNVII) Glossopharyngeal n. Neurogenic KCS: Lesions in Floor of Middle Fossa and Greater Petrosal Nerve (Cranial to Geniculate Ganglion)

 E.g. erosive or neoplastic lesions

 Similar findings to maxillary branch petrous temporal bone ophthalmic branch lesion, but no facial nerve mandibular branch paresis/paralysis trigeminal ganglion  If lesion after branching trigeminal n. of trigeminal nerve, eyelid anesthesia will be Major petrosal n. Facial n. predominately lateral lid (i.e. maxillary division, Geniculate ganglion zygomatic nerve) Neurogenic KCS: Lesions in Extraperiobital Sheath and Pterygopalatine Ganglion  E.g. temporal mm. myositis, cellulitis, abscesses from foreign body in orbit, dental Branches to zygomaticotemporal n.

apical abscesses, n. of pterygoid canal iatrogenic  if preganglionic = KCS, xeromycteria, anesthesia of eyelids Caudal nasal n.  if postganglionic = more pterygopalatine likely to have KCS and ganglion anesthesia of eyelids with no xeromycteria or vice versa Neurogenic KCS: Lesions in Periobita and Zygomaticotemporal Nerve

 i.e. with orbital trauma  KCS, periocular

anesthesia without Zygomaticotemporal n. xeromycteria Neurogenic KCS: Associated Findings

 Xeromycteria  Horner syndrome  Facial nerve paralysis  Eyelid anesthesia  Corneal anesthesia (neurotropic keratitis) Diagnostic Principles in Neurogenic KCS  Consider neurogenic KCS first if xeromyceteria  Otoscopy in all cases of unexplained or unilateral KCS  Schirmer tear test in all cases of otitis media/interna, Horner syndrome  Examine eyelids and cornea for anesthesia in all cases of unexplained or unilateral KCS Denervation Hypersensitivity and Lacrimal Gland

 oral pilocarpine to maximum tolerable level: – 2 drops/2%/2x day/10kg in increasing dose until toxicity, then decrease to previous dose Petrous Temporal Bone

Major petrosal n. Trigeminal n. Abducens n.

Facial n. Vestibular n. Cochlear n.

Glossopharyngeal n. Petrous Temporal Bone

 Pass through:  Possible effects on: – CN V – lacrimation – CN VII – nasal secretion – CN IX – blinking – sympathetic fibers – third eyelid retraction – parasympathetic fibers – eyelid and corneal  Proximity to: sensation – pupil – trigeminal ganglion (rostral PTB) – salivary secretion – CN VI (rostral PTB) Petrous Temporal Bone Lesions (e.g. otitis media/interna)

 xeromycteria (CN VII)  xerostomia (CN VII, CN IX)  facial palsy (CN VII)  facial and nasal cavity anesthesia (CN V)  loss of taste (CN VII, CN IX)  Horner syndrome – many idiopathic Horner syndrome and neurogenic KCS may be subclinical otitis media