Chapter-09 Cranial Nerves

BOOK TITLE: Neurology

1. Kenkre Rajendra B
Publishing Year
Author Affiliations
1. Goa, India
Chapter keywords


Olfactory nerve anosmia is commonly caused by trauma and fracture, cribriform plate of the ethmoid bone other causes are Korsakoffs syndrome thalamic lesion Alzeihmers disease, Parkinson disease, tumors-olfactory groove meningiomas, Glioma of the Frontal Lobe Carcinomatosis of the Meninges. Olfactory Hallucinations may be manifestation of complex partial seizures. Optic nerve, Blood supply. There occurs an area of watershed between central retinal artery (Ophthalmic) and posterior ciliary arteries (external carotid) In 80% of individuals this area is above the dorsum sellae in 5% cases it is prefixed overlying anterior margin of sella and in the remaining percentage of population it lies over the Diaphragm sella. Near the optic chiasma the optic nerve is supplied by the carotid and anterior cerebral artery, proximally it is supplied by the ophthalmic artery. Lateral geniculate body is supplied medially by anterior choroidal artery and laterally posterior choroidal artery. Optic radiations are supplied by middle cerebral and posterior cerebral artery. Ischaemia of the Chiasm occurs either due to pressure of the aneurysm or clipping central retinal artery. Emboli arise from Carotid atheroma, arch of the aorta and heart valves. Ischemic optic neuropathy. Sudden loss of vision no recovery, flame shaped hemorrhages in the edematous region of the disk. Papilloedema. Another important condition affecting the optic nerve is delayed effect (1-5 ) years of X-RT which affects the endothelium. Causes of 3rd nerve damage: Trauma, Neoplasms, Muscular Dystrophy, Mitochondrial disease, neuromuscular disease, infections, diabetes, Wernicke Korsakoff’s syndrome Miller Fisher syndrome variation of Guillian Barre syndrome, chronic inflammatory demyelinating Neuropathy, Trochlear nerve Lesion. Arteritis, Diabetes, Granulomas, Lambert Eaton syndrome, syphilis, Herpes Zoster superior cerebellar artery stroke. Abducens Nerve Lesions, Fracture at the base of the brain, fracture of the temporal bone, Neoplasms primary, metastatic, Gradenigo’s syndrome, Multiplesclerosis, CIDP. Trigeminal Nerve Lesions: Dental treatment surgical trauma, tumors schwanncell origin trigeminal Neuroma. Nasopharyngeal cancer, Wallenbergs syndrome cavernous sinus Aneurysm, internal carotid artery aneurysm, Trigeminal Neuralgia usually idiopathic, in young people it may be manifestation of multiple sclerosis, Syphilis: Lateral sinus Thrombosis, syringobulbia, Brainstem glioma. The lesion may affect all divisions of Trigeminal Nerve or one or two divisions in isolation. Seventh nerve Facial nerve Bell’s Palsy: Common Neurological disorder, Acute Lower Motor Neuron Facial Palsy. Predisposing causes include diabetes, hypertension, steroids in doses of 30 mg if started early and continued for 2 weeks are helpful in hastening the recovery which may occur within 2 to 6 months. Herpes zoster syndrome, Ramsay Hunt syndrome eruption of vesicles around external auditory meatus and over the mastoid process. Lower motor neuron palsy. Upper motor neuron facial weakness, internal capsule infarction, lacunar infarction, tumor cerebral hemispheres such as glioma, meningioma when the nerve is affected at the nucleus fascicle by head trauma, infection such as tuberculosis, basal meningitis, syphilis, associated features are 5th, 6th nerve palsies. VIIIth cranial nerve acoustic neuroma: it originates from the vestibular portion of VIIIth Nerve in the internal auditory canal. It is characterized by progressive sensorineural hearing loss, vertigo, ipsilateral unsteadiness if V, VI, VII nerves affected weakness and loss of taste anterior 2/3 tongue and sometimes decreased corneal reflex. If tumor extends posteriorly cranial nerve IX may be involved resulting in dysphagia and absent pharyngeal reflex, involvement of cranial nerve X may result in hoarseness where as the involvement of XI cranial nerve may result in the weakness of muscles like trapezius and sternomastoid Romberg’s sign and finger nose finger test may be positive. Nystagmus is horizontal, rotatory fast component of nystagmus to opposite side may be present. Vagus Nerve, Jugular foramen syndrome: Since IX, X and XI nerve exit the cranial vault through the jugular foramen damage to the nerves due to tumor basal meningitis compromises functions of these nerves; symptoms include loss of taste in the posterior two third of the tongue, paralysis of the vocal cords, palate, pharynx and paralysis of the trapezius and sternomastoids.

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