Cranial nerve injury Notes

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This Osmosis High-Yield Note provides an overview of Cranial nerve injury essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Cranial nerve injury by visiting the associated Learn Page.
NOTES NOTES CRANIAL NERVE INJURY GENERALLY, WHAT IS IT? PATHOLOGY & CAUSES ▪ Brain/cranial nerves injury → neurological dysfunction CAUSES ▪ Trauma (accidental, inflicted), autoimmune, infectious, idiopathic SIGNS & SYMPTOMS ▪ Varies widely ▫ Area-dependent DIAGNOSIS DIAGNOSTIC IMAGING CT scan/MRI ▪ Specific, focused neurological functioning tests TREATMENT ▪ Symptomatic complications, treat underlying causes BELL'S PALSY osms.it/bells-palsy PATHOLOGY & CAUSES ▪ Lower motor neuron weakness of cranial nerve VII (facial nerve) → acute, peripheral facial palsy ▪ Adversely affects facial motor activity; lacrimal, salivary glands (parasympathetic fibers); taste (afferent fibers on anterior two-thirds of tongue); external auditory canal, pinna (somatic afferents) ▪ Etiology unknown ▫ Potentially viral-associated ischemia, demyelination (e.g. herpes zoster, herpes simplex (HSV), Epstein–Barr virus, Lyme disease) 552 OSMOSIS.ORG RISK FACTORS ▪ Age (peak incidence > 50), diabetes mellitus, pregnancy (third trimester), early postpartum COMPLICATIONS ▪ Corneal exposure → keratitis, motor regeneration → oral incompetence, reinnervation “miswiring” → synkinesis (involuntary muscle movement) ▪ Incomplete sensory regeneration ▫ Dysesthesia (unpleasant/abnormal touch), dysgeusia (distorted taste), ageusia (decreased taste)
Chapter 71 Cranial Nerve Injury SIGNS & SYMPTOMS ▪ Unilateral facial weakness evolves rapidly over 48 hours ▫ Eyebrow sags, eye won’t close, mouth corner droops (drooling, difficulty eating/ drinking), decreased tear production → ocular dryness, hyperacusis (↓ everyday sound tolerance), ageusia (decreased taste sensation) ▪ Prodromal symptoms (pre-onset) ▫ Ear pain, dysacusis (sound distortion) ▪ See mnemonic: BELL’S Palsy MNEMONIC: BELL'S Palsy Symptoms of Bell’s palsy Blink reflex abnormal Ear sensitivity Lacrimation: deficient, excess Loss of taste Sudden onset Palsy: CN VII nerve muscles (All symptoms are unilateral) DIAGNOSIS LAB RESULTS ▪ Serologic testing if viral infection suspected OTHER DIAGNOSTICS ▪ House–Brackmann facial nerve dysfunction classification ▫ Grades facial muscle impairment degree ▫ Normal, mild, moderate, moderatelysevere, severe, total paralysis ▪ Palpebral-oculogyric reflex (Bell phenomenon) ▫ Attempted eyelid closure → upward eye deviation ▪ Stethoscope loudness test ▫ Individual listens to tuning fork through stethoscope ▫ Hyperacusis indicates paralyzed stapedius muscle on affected side ▪ ↓ pinprick sensation in posterior auricular area ▪ ↓ taste ▫ Sweetness, saltiness, acidity ▪ Motor nerve conduction studies (NCS) ▫ Estimates axonal loss degree TREATMENT MEDICATIONS ▪ Corticosteroids ▫ Symptom onset → begin within 3–4 days OTHER INTERVENTIONS ▪ Artificial tears, eye patching ▫ Reduce corneal damage risk ▪ Physical therapy (e.g. facial exercise, neuromuscular retraining) ▪ May resolve spontaneously within three weeks Figure 71.1 An individual with Bell’s palsy affecting the right side of the face. OSMOSIS.ORG 553
TRIGEMINAL NEURALGIA osms.it/trigeminal-neuralgia PATHOLOGY & CAUSES DIAGNOSIS ▪ AKA tic douloureux; stimulating facial trigger zone → intense, stabbing, paroxysmal pain in trigeminal nerve (cranial nerve V—usually V2/V3 subdivisions) ▫ Triggers: touching/moving tongue, lips, face; chewing; shaving; brushing teeth; blowing nose; hot/cold drinks DIAGNOSTIC IMAGING TYPES OTHER DIAGNOSTICS ▪ Classic ▫ Most common; unknown etiology, artery/vein compressing cranial nerve (CN) V root may → pain ▪ Secondary ▫ Nonvascular lesion compressing nerve → pain RISK FACTORS ▪ Biological sex (female > male) ▪ Age (peak incidence 50–60) ▪ Demyelinating disorders (e.g. multiple sclerosis) ▪ Postherpetic trigeminal neuropathy ▪ Acoustic neuroma ▪ Saccular aneurysm ▪ Vestibular schwannoma SIGNS & SYMPTOMS ▪ Pain paroxysms ▫ Last one–several seconds; may repeat; usually unilateral ▪ Dull pain between paroxysms ▪ Facial muscle spasms/autonomic symptoms (e.g. lacrimation, diffuse conjunctival injection, rhinorrhea) 554 OSMOSIS.ORG CT scan/MRI ▪ May identify lesion/vascular compression ▪ Electromyographyrigeminal reflex testing ▫ Measures muscles’, controlling nerves’ electrical activity ▪ Classic trigeminal neuralgia ▫ No clinically evident neurologic deficit, no better explanation via another diagnosis, ≥ three attacks of unilateral facial pain fulfilling criteria A and B ▫ A: Occurs in ≥ one trigeminal nerve divisions, no radiation beyond trigeminal distribution ▫ B: Pain has three or more of the following four characteristics: recurring paroxysmal attacks (< two minutes); severe intensity; shock-like, shooting, stabbing, sharp pain; stimulating affected facial side → > two attacks (other attacked may be spontaneous) TREATMENT MEDICATIONS ▪ Pain management SURGERY ▪ Microvascular decompression ▪ Neuroablation ▫ Rhizotomy with radiofrequency thermocoagulation/mechanical balloon compression/chemical (glycerol) injection ▫ Radiosurgery ▫ Peripheral neurectomy, nerve block

Osmosis High-Yield Notes

This Osmosis High-Yield Note provides an overview of Cranial nerve injury essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Cranial nerve injury by visiting the associated Learn Page.