Ectoparasites

Ectoparasites

* What are ectoparasites?
o Insects and arachnids which feed through or upon the skin
* How do they affect human health?
o Transmit disease
o Cutaneous irritation
o Allergic reaction

Biological Classification of Ectoparasites
* Superkingdom Eucaryotae
* Kingdom Animalia
* Phylum Arthropoda
o Class Insecta
o Class Arachnida

Bedbugs
* Class Insecta
* Family Cimicidae
* Order Hemiptera
* Genus Cimex
o Cimex lectularius
o Cimex hemipterus

Bedbugs - Data
* Size = 4-5 mm long/3 mm wide
* Color = varies with maturity and feeding state
o Adult = reddish brown
o Nymphs = yellowish white
* Other names = chinches, wall lice, red coats
* Feeding Apparatus – long sharp proboscis extends from anterior head into a groove under the thorax
* Feeding Pattern – nocturnal, gregarious, blood feeder
* Reproduction – fertile adult female lays yellowish-white eggs
o Eggs hatch into nymphs in 37 – 128 days depending on temperature
* Habitat – places where they can easily access humans at night
o Wood bedsteads, mattresses, loose wall paper, under rugs, etc

Bedbug - Epidemiology
* Distribution – bedbugs move from one human residence to another in various ways
o Water pipes
o Adjacent walls
o Clothing
o Travel bags/luggage
o Laundry
o Furniture

Bedbugs- Health Effects
* Bedbugs have never been associated with any disease transmission
o Their effect on humans is tied to the reaction to the bites
o Reaction varies with the individual
o Most severe reaction are due to cutaneous puncture and the effect of the salvia
+ Causing swelling (welts), irritation, allergic inflammation

Mosquitoes
* Class Insecta
* Order Diptera
* Family Culicidae
* Genus Aedes
* Genus Anopheles
* Genus Culex
* Genus Psorophora

Mosquitoes - Data
* Size = 3 – 5 mm long;
o A few species are much larger = 9 mm long
* Color – dark interspersed with while bands
* Females are blood feeders while males are plant feeders
o Females only mate once; then produce fertile ova for life
o Mosquito life expectancy ~ 5 weeks

Mosquitoes – Life Cycle
* Egg
o Female mosquitoes lay their eggs (oviposit) in aquatic settings
o Standing water, tree holes, buckets, tires, etc
o Generally do not oviposit in large bodies of water like lakes
* Larvae – aquatic life stage
o Hatches from eggs and actively feeds on aquatic debri
* Pupae – aquatic life stage
o Developmental stage – metamorphosis – not feeding
* Adults – male and female

Mosquitoes – Health Effects
* Biological Vectors of Disease Pathogens
o Yellow Fever
o Dengue Fever
o Malaria
o Encephalitis
o Microfilariae = nematode larvae
* Mechanical Vectors of Disease Pathogens

Ticks
* Class Arachnida
* Order Acarina
* Family Ixodidae – hard ticks
* Genus Dermacenter
* Genus Amblyomma
* Genus Ixodes
* Genus Rhipicephalus

Tick Data
* Blood feeders – sole source of nutrients
o All vertebrates esp. mammals are hosts for ticks
o Heavy infestations result in significant blood loss
+ Some ticks ingest up to 2 gms of blood per feeding
+ Both male and female feed
* Ticks have longevity- live many years
o Ixodid ticks may live from 7-21 years
o This increases their role as reservoirs for pathogens

Ticks – Health Effects
* Dermatosis – inflammation at bite site
* Envenomization – toxic effect of tick salvia
* Exsanguination – loss of much blood
* Tick Paralysis – damage to peripheral nerves by the bite
* Otoacariasis – damage in the auditory canal
* Disease transmission – vectors of microbial pathoges

Tick - Life Cycle
* Four life stages – tick life history
o Egg – fully engorged females may lay up to 18,000 eggs
o Larva – hexapod, having six legs
o Nymph – sexually immature octapod, eight legs
+ Only one nymphal stage in Ixodid ticks
o Adult – sexually mature
* Host animals
o Some ticks have many hosts, some only one
o Host animal may change with development stage
o Some ticks may molt as many as five times; requiring a different host for each molt
* Ticks sometimes transmit pathogens transovarially

Ticks- Vectors of Microbial Diseases
* Bacterial Disease Transmission
o Rocky Mountain Spotted Fever
+ Dermacentor variabilis – American Dog Tick
+ Amblyomma americanum – Lone Star Tick
o Tularemia
+ Amblyomma americanum
o Lyme Disease
+ Ixodes ricinus
* Viral Disease Transmission
o Tick-Borne Encephalitis
o Colorado tick fever

Sucking Lice
* Class Insecta
* Order Anoplura
* Family Pediculidae
* Genus Pediculus
* Genus Pthirus

Sucking Lice Data
* Blood sucking ectoparasites of mammals
* Flat-bodied with no wings
o Legs adapted for clinging to hair and feathers
o 1.5 – 3.0 mm in length
* Six families having medical or veterinary importance
o One of these contains the species that affect humans
* Significant Human Lice
o Pediculus humanus capitis – head louse
o Pediculus humans humunas – body louse
o Pthirus pubis – pubic (crab) louse

Louse – Life Cycle
* Egg
* Nymphs
* Adults – male and female
o Female may lay 250- 300 eggs per day for 30 days

Sucking Lice – Health Effects
* Bacterial Disease Transmission
o Epidemic Relapsing Fever
+ Borrelia recurrentis
o Epidemic Typhus Fever
+ Rickettsia prowazeki
o Murine Typhus Fever
+ Rickettsia typhi
o Trench Fever
+ Rickettsia quintana

Biting Lice
* Class Insecta
* Order Mallophaga
* Family – there are no families of biting lice

that affect humans health in the world
Most are ectoparasites of birds

Mites
* Class Arachnida
* Order Acarina
* Family Dermanyssidae
* Genus Liponyssoides
* Genus Dermanyssus
* Class Arachnida
* Order Acarina
o Suborder – Trombidiformes
* Family Trombiculidae
* Genus Trombicula

Trombiculid Mites = Chiggers
* Eggs – hatch one week
* Larva – six legged
o Only parasitic stage in this family
o Not host specific – feeds on many hosts
o Leaves host when fully fed or engorged
* Nymph – eight legged
o Live in the soil and feed on insect eggs and soil debri
* Adult – eight legged
o Live in the soil and feed on insect egges and soil debri
o Male and females
o In North American – 1 -2 generations per year

Chigger Dermatitis
* Larval mites – chiggers- do not burrow into the skin
* Larval mites – chiggers – do not suck blood
o They attach to the surface of the skin or at the base of hairs and inject a digestive fluid into the tissues which lyses cells
o They ingest the cell fragments and cellular contents
* The digestive fluid causes the bite to itch
* Common North American Chiggers
o Trombicula alfreddugesi
o Trombiula splendens
o Trombicula batatas

Mites- Vectors of Microbial Pathogens
* Scrub Typhus
* Rickettialpox
* Hemorrhagic Fevers

Fleas
* Class Insecta
* Order Siphonaptera
* Family Pulicidae
* Genus Pulex
o Pulex irritans – human flea
* Genus Tunga
* Genus Ctenocephalides

Flea Data
* Blood sucking ectoparasites of vertebrates
* No wings – do not fly
* Adapted for jumping – strong posterior legs
* Many hosts
* Larvae feed on debri within the nest of the host

Flea – Life Cycle
* Egg – large in comparison to the adult flea
o Hatch in 9 – 15 days under ideal conditions
* Larva – small worm-like organisms which feed on dried blood, cutaneous and fecal debri
* Pupa – inactive, quiet stage, contained within a coccoon
* Adult – laterally compressed, wingless, legs adapted for jumping
o Piecing-sucking mouthparts
o Life expectancy –starved- 100 -125 days
o Life expectancy – fed – 500 – 600 days

Fleas – Health Effects
* Disease transmission
o Plague
o Murine typhus
o Myxomatosis in rabbits
o Cestode intermediate host
* Cutaneous infestation
o Adult flea burrows into skin
+ Chogoe flea of humans – Tunga penetrans

Fly Larvae
* Myaisis
o Infestation with the larvae of diptera or flies
o Cutaneous
o Intestinal
o Urogenital
Leeches

Ectoparasites.ppt

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Human CytomegaloVirus

Human CytomegaloVirus - Characteristics
* ubiquitous among HerpesViruses
* lymphotrophic
* largest genome of all Herpes Viruses
* replicates only in human cells
+ permissive cells include fibroblasts, epithelial cells, and macrophages
+ semipermissive cells include mononuclear lymphocytes, the stromal cells of the bone marrow, and others = basis of latency
+ Infected cells become significantly enlarged = cytomegaly
* Highly species-specific
+ Only infected humans
+ There are cytomegaloviruses specific for other animals

CytomegaloVirus - Pathogenesis

* Replicative Cycle is the same as other herpeviruses
+ replication occurs in epithelial cells and virus is shed into most body fluids
+ virus then infects cells like lymphocytes and macrophages
# virus is highly cell-associated and is transmitted by these cells
# Envelope glycoprotein protects virus from host antibody
* Binds Fc portion of immunoglobulins
* Virus establishes latent infection in monouclear cells and in organs such as kidney, liver, heart; fibroblasts and mononuclear cells in these organs
+ reactivation due to various factors including imunosuppression
+ reactivation sheds virus into body fluid including semen, breast milk, and urine
+ also reactivation often follows blood transfusion and organ transplants

Human CytomegaloVirus – Clinical Diseases

* asymptomtic infection
+ in most healthy individuals infection may occur without symptoms
+ however, virus is shed; these people are healthy carriers
+ if symptoms develops they appear as mononucleosis or hepatitis
* Mononucleosis-like syndrome
+ much like EBV with atypical lymphocytosis
+ mild pharyngitis and variable lymphadenopathy
+ heterophile antibody negative
* Hepatitis = liver dysfunction similar to hepatitis, but no evidence of classical hepatitis viruses
* Cytomegalic Inclusion Disease
+ Congenital
+ Perinatal

CMV– Cytomegalic Inclusion Disease
Human CytomegaloVirus – Risk Factors
CytomegaloVirus - Epidemiology

* Cytology
+ hallmark of CMV infection is the “cytomegalic cell” ; an enlarged cell in which the nucleus contains a dense, central, basophilic intranuclear inclusion body; often looks like an “owls eye”
+ infected cells may be found in any tissue and in urine
+ Papaicolaou or hematoxylin-eosin stains
* Antigen Detection Rapid and Sensitive Tests
+ Antigen detection using enzyme or fluorescent labeled monoclonal antibody
+ Nucleic acid detection using similarly labeled DNA probes
* Serology
+ Seroconversion,(antibody response) in an excellent marker for primary infection(IgM) or recurrent infection(IgG)
* Culture
+ CMV grows in diploid-fibroblast cell cultures
+ characteristic CPE observed in 4 - 6 weeks
+ not routinely used for diagnosis; much used epidemiologically

Human Herpes Virus, Type 6
Human Herpes Virus, type 6 – Roseola
Human Herpes Virus, type 6 - Epidemiology
ParvoViruses - Characteristics
ParvoViruses- Virus Cycle
ParvoViruses - Pathogenesis
Human Parvovirus, B19 – Erythrema infectiousm
Erythrema infectiosum; Fifth’s Disease
ParvoViruses – Other Clinical Diseases
ParvoVirus, B19 - Diagnosis
ParvoVirus, B19 - Epidemiology
ParvoVirus- Control
PoxViruses - Characteristics
PoxViruses – Clinical Diseases
Molluscum contagiosum – Clinical Disease
Small Poxvirus - Epidemiology
* Human Reservoir
o Respiratory droplets
o Scabs from lesions
* Most common mode of transmission
o Person-to-Person, direct, respiratory droplet

Smallpox - Control
* Active Attenuated Vaccine – chemically stabilized
o Vaccinia Virus– naturally attenuated zoonotic strain
+ Obtained from vesicular lesion of calves
+ Later virus were grown in chicken embryos
o From early experiment conducted by Edward Jenner -1796
* First microbial disease to be eradicated via herd immunity from a vaccine
o Routine vaccination in the U.S ceased in 1971
o Routine vaccination in the World ceased in 1978
* Epidemiology/Control
o The importance of smallpox today is that it is and example of the disease which was eradicated by producing “herd immunity” through the process of vaccination( use of active vaccinia virus)


Human CytomegaloVirus.ppt

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Facial Nerve Paralysis

Facial Nerve Paralysis
By: Vanessa S. Rothholtz, M.D., M.Sc.
UCI Department of Otolaryngology - Head and Neck Surgery


Chief Complaint
My Starbucks caramel macchiatto dribbled down my chin this morning, and it ruined my white coat. Now my face isn’t working. Do I need a face lift?
History
* Unilateral left-sided otalgia (TMJ)
* Fever, chills
* Headache
* Generalized fatigue
* Conjunctivitis two weeks ago (resolved with antibiotics)
* “My eczema acted up again last week, but it looked a little different.”
* Travel – Sonoma County for a friend’s wedding a last month

Physical
* Eyes: Left eye with injected conjunctiva, pupils equal and reactive
* Ears: EAC patent, TM c/m/i
* Nares: Patent, clear
* OC/OP: Dentition intact, tongue midline / mobile, No tonsillar hypertrophy
* Face:
o Normal tone and symmetry at rest
o Obvious facial asymmetry with effort
o No perceptible forehead movement
o Incomplete eye closure
o Asymmetrical motion of mouth with maximal effort

What grade of paralysis is this based on the House-Brackmann facial nerve grading scale?

House-Brackmann Facial Nerve Grading Scale

I Normal
II Normal tone and symmetry at rest

Slight weakness on close inspection

Good to moderate movement of forehead

Complete eye closure with minimum effort

Slight asymmetry of mouth with movement

III Normal tone and symmetry at rest

Obvious but not disfiguring facial asymmetry

Synkinesis may be noticeable but not severe

+/- hemifacial spasm or contracture

Slight to moderate movement of forehead

Complete eye closure with effort

Slight weakness of mouth with maximum effort


IV Normal tone and symmetry at rest

Asymmetry is disfiguring or results in obvious facial weakness

No perceptible forehead movement

Incomplete eye closure

Asymmetrical motion of mouth with maximum effort

V Asymmetrical facial appearance at rest

Slight, barely noticeable movement

No forehead movement

Incomplete eye closure

Asymmetrical motion of mouth with maximum effort

Differential Diagnosis
V Anomalous sigmoid sinus, benign intracranial hypertension, intratemporal aneurysm of internal carotid artery, embolization for epistaxis (external carotid artery branches)

I Malignant otitis externa, otitis media, cholesteatoma, mastoiditis, meningitis, parotitis, chicken pox, Ramsay Hunt syndrome, encephalitis, poliomyelitis (type I), mumps, mononucleosis, leprosy, HIV/AIDS, influenza, Coxsackie virus, malaria, syphilis, scleroma, TB, botulism, mucormycosis, Lyme disease

T Cortical injuries, basilar skull fractures, brainstem injuries, penetrating injury to middle ear, facial injuries, altitude paralysis (barotrauma), SCUBA diving (barotrauma)

A Temporal arteritis, periarteritis nodosa, Multiple sclerosis, myasthenia gravis, sarcoidosis, Wegener granulomatosis, eosinophilic granloma

M Paget disease, osteopetrosis, diabetes mellitus, hyperthyroidism, pregnancy, alcoholic neuropathy, bulbopontine paralysis, oculopharyngeal muscular dystrophy

I Bell palsy, Melkersson-Rosenthal syndrome (recurrent facial palsy, furrowed tongue), hereditary hypertrophic neuropathy, (Charcot-Marietooth disease, Dejerine-Scottis disease), Landry-Guillain-Barre syndrome, Sarcoidosis, Kawasaki disease, surgery, embolization

N Acoustic neuroma, glomus jugulare tumor, leukemia, meningioma, hemangioblastoma, hemangioma, pontine glioma, sarcoma, hydradenoma, gacial nerve neuroma, teratoma, fibrous dysplasia, von Recklinghausen’s disease, carcinomatous encephalitis, cholesterol granuloma, carcinoma (invasive or metastatic)

C Molding, forceps delivery, myotoic dystrophy, Moebius syndrome

D Vaccine for rabies, Antitetanus serum, mandibular block anesthesia

Course of the Facial Nerve
* Intracranial – Arises at the pontomedullary junction and courses with CNVIII to the internal acoustic meatus - 12mm
* Meatal – Anterior to the superior vestibular nerve and superior to the cochlear nerve – 10mm
* Intratemporal –
o Labyrinthe segment
+ Passes through narrowest part of fallopian canal - 12mm
+ Narrowest part of facial nerve. The most susceptible to compression secondary to edema.
o Tympanic segment
+ From geniculate ganglion to pyramidal turn – 11mm
o Mastoid segment
+ Exits the stylomastoid foramen – 13mm
* Extracranial – From stylomastoid foramen to pes anserinus
The longest segment of the facial nerve is:

A. Vertical of mastoid portion

B. Cisternal portion

C. Tympanic portion

D. Portion in the IAC


Blood supply to facial nerve – clinical relevance
* Courses between the epineurium and periosteum – making the blood supply at risk when mobilizing at the first genu
* Extrinsic
o Stylomastoid artery (branch of the postauricular artery of external carotid artery)
o Greater petrosal artery (branch of middle meningeal artery)
o Internal auditory artery (branch of the AICA)
* Labyrinthe segment - lacks anastomosing arterial cascades thereby making the area vulnerable to ischemia
Work Up

* Basic labs, thyroid function panel, Lyme titers ELISA for antibodies
* Audiogram
* Stapedial reflex
* EKG
* MRI with gadolinium / CT
* Nerve Excitability Test, Maximal Stimulation Test, Electroneuronography (EnoG) - Useful 72 hours post-injury

Topognostic Testing
* Schirmer test for lacrimation
* Stapedial reflex test (stapedial branch)
* Taste testing (chorda tympani nerve)
* Salivary flow rates and pH (chorda tympani)
Schirmer Test
* Greater superficial petrosal nerve
* Filter paper is placed in the lower conjunctival fornix bilaterally
* 3- 5 minutes
* Value of 25% or less on the involved side or total lacrimation less than 25 mm is considered abnormal.
Stapedial Reflex
* Stapedius branch of the facial nerve
* Most objective and reproducible
* A loud tone is presented to either the ipsilateral or contralateral ear  evokes a reflex movement of the stapedius muscle  changes the tension on the TM (which must be intact for a valid test) resulting in a change in the impedance of the ossicular chain
* If intact stapedial reflex, complete recovery can be expected to begin within six weeks
* Absence of the stapedial reflex during the first two weeks in Bell’s Palsy is common


Taste Testing
* Chorda tympani
* Extremely subjective
* Papillae generally disappear within 10 days post injury - middle 1/3 of the tongue is most indicative, because the anterior 1/3 may receive bilateral input.

Salivary flow rates
* Chorda tympani
* Cannulation of Wharton's ducts bilaterally
* 5 minute measurement of output
* Significant if 25% reduction in flow of the involved side as compared to the normal side
* Salivary pH Flow Rate
Nerve Excitability Test (NET)
* Most predictive prognostic factor for recovery of facial nerve function*
* Hilger nerve stimulator over stylomastoid foramen
* Reflects elevated thresholds for neuromuscular stimulation due to degeneration / disruption of axons (comparison to contralateral side)
* Difference > 2.5 milliamps - poor prognosis

Nerve Excitability Test (NET)
* Benefits:
o Easy to perform
o More comfortable for patient
* Drawbacks
o Subjectivity (relies on operator’s visual detection of response)
o May exclude smaller fibers (current thresholds are likely to selectively activate larger fibers with lower thresholds and not those smaller fivers closer to stimulating electrode)

Maximal Stimulation Test (MST)
* Electrical impulse administered to saturate the nerve with current and to compare it to contralateral side
* Test is repeated periodically until definitive response
* Response
o Equivalent to contralateral side
o Minimally diminished (50%)
o Markedly diminished (< 25% of normal)
o Absent
* Symmetric response within first ten days – complete recovery in > 90%
* No response within first ten days – incomplete recovery with significant sequelae
* Superior to NET - test becomes abnormal sooner, but drawback is subjectivity
Evoked electromyography (EEMG) or Electroneuronography (EnoG)
* Records compound muscle action potential (CMAP) with surface electrodes placed transcutaneously in the nasolabial fold (response) and stylomastoid foramen (stimulus)
* Waveform responses are analyzed to compare peak-to-peak amplit`udes between normal and uninvolved sides where the peak amplitude is proportional to the number of intact axons
* Most reliable in first 2-3 weeks post event (as neuropraxic fibers recover or regenerate, they discharge asynchronously and the response is subsequently diminished)
* Response < 10% of normal in first 3 weeks – poor prognosis
* Response > 90% of normal within 3 weeks of onset – 80-100% probability of recovery
* Testing every other day
* Advantages: Reliable
* Disadvantages:
o Uncomfortable
o Cost
o Test-retest variability due to position of electrodes
Electromyography (EMG)
* Measures post-synaptic membrane di/triphasic (polyphasic) potentials with voluntary muscle contraction that are present 6-12 weeks prior to visible return of function
* Assesses reinnervation potential of muscles two weeks after onset
* Limited value early in evaluation because fibrillation potentials indicating axonal degeneration do not appear until 10 – 14 days post onset
* Detection of motor units in 2 of 3 muscle groups – 87% satisfactory outcome
* Detection of motor units in 1 muscle group – 11% satisfactory
More Methods
* Antidromic (retrograde) Conduction – F-waves represent activated motor neurons in facial muscles.
* Transcranial magnetic stimulation – Enables central activation via a transcranial application of induce current via an electromagnetic coil
* Trigeminofacial Reflex – Records action potentials reflexively generated in the orbicularis oculi muscle in response to an electrical stimulus applied to V1
Lyme Disease - Borrelia Burgdorferi

* Ten percent of patients have facial nerve paralysis after 1-4 weeks incubation period
* ELISA to search for IgG and IgM antibodies
* Facial paralysis resolves in 6 to 12 months
* Treatment
o Early antibiotics
# Reduce symptoms
# Event long-term sequelae
o Children - IV penicillin, ceftriaxone or cefotaxime
o Adults - tetracycline
o Muscular therapy
Bell’s Palsy
* 60-70% cases
* Pathophysiology – Impaired “axoplasmic” flow from edema of facial nerve within fallopian canal
* Rapid onset and evolution < 48 hours
* May be associated with acute neuropathies of cranial nerves V- X
* Pain or numbness affecting ear, mid-face, tongue and taste disturbances
* Recurrences are more likely (2.5x) in patients with family history, immunodeficiency or diabetes
Bell’s Palsy Treatment
* Oral antivirals - Acyclovir - 10mg/kg (500mg) q8hrs x 7 days
* Corticosteroid taper 1mg / kg / day for 10 days
* Eye protection - lacrilube
* Follow progression with serial exams
* Facial nerve decompression
+ Progression to > 90% degeneration on ENOG
+ Performed before irreversible injury to the endoneural tubules occurs (two weeks), will allow for axonal regeneration to occur
Treatment of Bell’s Palsy with Steroids: A controversial closer look
* Steroids may have the following effects:
o Reduce risk of denervation
o Preventing / lessening synkinesis
o Preventing progression to complete paralysis
o Hastening recovery
* Controversy:

Ramsay Hunt Syndrome
Herpes Zoster Oticus (Ramsay Hunt syndrome)
* 10-15% of acute facial palsy cases
* Lesions may involve the external ear, the skin of EAC or soft palate
* Associated symptoms – hearing loss, dysacusis and vertigo
* Additional involvement of CN V, IX and X and cervical branches 2, 3 and 4
* Pathogenesis – Neural injury due to edema at point between the meatal foramen and the geniculate fossa in the labyrinthe segment
Acute Otitis Media
* History and physical exam make the diagnosis
* Palsy is progressive over 2 to 3 day period
* Infectious agent – Staphylococcus non-aureus, Propionobacterium
* CT temporal bone
* Treatment
o Myringotomy
o Otic antibiotic drops containing topical steroids
o IV antibiotics and steroids
o If not improved… mastoidectomy
Möbius Syndrome
* Most frequently sporadic
* Congenital facial weakness with impairment of ocular abduction
* Dysfunction of other cranial nerves – III, IV, IX, X, XII
* Skeletal abnormalities (orofacial, limb malformations)
* Pathogenesis – Genetic cause vs. Ischemic cause
Melkersson-Roenthal syndrome
* Triad
* Lips become chapped, fissured and red-brown in appearance
* Biopies identify granulomatous changes
* Facial nerve decompression may be indicated if facial paralysis is severe and recurrent
Neoplastic

* About 5% of cases of facial nerve paralysis are caused by tumors
* Characteristics of facial nerve palsy
+ Slow developing
+ Additional cranial nerve deficits
+ Recurrent ipsilateral involvement
+ Adenopathy
+ Palpable neck or parotid mass
* Most common benign tumor - facial nerve schwanomma
* Most common malignant tumors - mucoepidermoid carcinoma and adenoid cystic carcinoma of the parotid gland.

Temporal Bone Fractures
* Longitudinal fractures
o 80% incidence but 10-20% with facial nerve injury
* Transverse fractures
o 20% incidence, but 50% with facial nerve injury
* Most common site of fracture
o Perigeniculate region
* Penetrating injury to extratemporal facial nerve branches
* Injuries medial to a line perpendicular to the lateral canthus do not need to be explored because they recover spontaneously (draw please)
* Immediate paralysis after injury lateral to this line needs to be explored and repaired with an end-to-end anastomosis 48-72 hours after the initial injury
Sunderland Nerve Injury Classification
* I Neuropraxia
o Conduction block from compression and loss of axonic flow
o Complete recovery
* II Axonotmesis
o Axon disrupted but endoneurium preserved
o Wallerian degeneration occurs distal to site of injury
o Complete recovery
* III Neurotmesis
o Complete disruption of axon including its surrounding myelin and endoneurium
o Wallerian degeneration
o Unpredictable outcome – High risk for synkinesis
* IV Complete disruption of perineurium
* V Complete disruption of epineurium
o Risk of a neuroma from nerve sprouts outside of nerve sheath

A patient with facial nerve injury following a gunshot wound to the temporal bone typically presents with which of the following symptoms?

A. Midface branch paralysis

B. Complete facial paralysis

C. Forehead paralysis

D. Partial weakness of the facial nerve

What if the facial paralysis doesn’t resolve?
* End-to-End Anastomosis
* Cable Nerve Graft
* Hypoglossa-Facial Nerve Anastomosis (Crossover or Jump Graft)
* Muscle transposition (Gracilis)
* Static Suspension (Gortex, Threads)

Complications

* Keratitis
* Emotional/Social Issues
* Synkinesis

Facial Nerve Paralysis.ppt

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