Cranial nerve injury Notes
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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
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