University:
American Career College
Course:
NURS-113 | Beginning Medical/Surgical Nursing
Academic year:

2018
Views:

337

Pages:

40
Author:

KillSteel

Cranial nerve disorders Introduction  Cranial nerve lesion may be in: The lesion may affect the nucleus of the cranial nerve within the brainstem  Lesion may damage the axons within the brainstem  In both;  Damage to nearby pathways through the brainstem---weakness, sensory loss or ataxia in the limbs. Introduction  Lesion may affect the nerve itself outside the brainstem as it passes to or from the structure which it supplies: Causes an isolated cranial nerve palsy or a cluster of palsies arising from adjacent nerves Lateral aspect of the brainstem and cranial nerves 3–10 and 12 Olfactory nerve • • • Not common Patients complain that they are unable to smell and that all their food tastes the same Common causes: • • • Nasal obstruction; infective or allergic Truama or tumour at the floor of the anterior fossa Idiopathic Olfactory nerve  Olfactory nerve bundles penetrate the thin cribiform plate to innervate the mucosa in the roof of the nasal cavity Optic nerve, chiasm and radiation The visual pathway and its common types of lesion Monocular blindness  Causes:        Thrombo-embolism in the ophthalmic artery Prodromal phase of migraine Infarction of the optic nerve or retina Giant cell arteritis Optic neuritis Methanol poisoning Tobacco–alcohol amblyopia Bitemporal hemianopia  Lesion in optic chiasma due to: Pituitary tumours (adenoma)  Aysmmetrical compression on optic nerve may occur  Homonymous hemianopia   Due to occipital infarction; posterior cerebral artery occlusion Capsular infarction Homonymous quadrantanopia   Lesions in the temporal region, affecting the lower parts of the optic radiation---- field loss in the contralateral upper quadrant Lesions in the parietal region---- field loss in the contralateral lower quadrant Oculomotor, Trochlear and Abducent nerves Action of individual eye muscles Action of individual eye muscles Third nerve palsy  Common causes:    Posterior communicating artery aneurysm Mononeuritis in diabetes (pupil usually normal) Cavernous sinus thrombosis Cavernous sinus Third nerve palsy Fourth nerve palsy  Fourth nerve palsy  Uncommon  Can be caused by trauma of the orbit Fourth nerve palsy Sixth nerve palsy   Common causes:    As a false localizing sign in raised ICP Pontine lesion Lesion in the cavernous sinus, superior orbital fissure Sixth nerve palsy Supranuclear gaze palsy Supranuclear gaze palsy    Common Site of lesion: contralateral cerebral hemisphere Causes: Massive stroke  Severe head injury  Gaze palsy; At the midbrain level   Uncommon Parinaud’s syndrome    Eyes won't move up or down in the vertical plane Eyes won't converge May be associated with ptosis and pupil abnormality Gaze palsy; At the pontine level   Uncommon Pontine lesion will cause voluntary and reflex paralysis of conjugate gaze towards the side of the lesion Internuclear ophthalmoplegia Internuclear ophthalmoplegia Internuclear ophthalmoplegia   Site of lesion: midbrain/pons Common cause: multiple sclerosis Other causes of abnormal eye movements Myasthenia gravis   Ocular involvement common in myasthenia gravis. Should be considered in any unexplained ophthalmoplegia Myopathy Common in Graves’ disease  Involvement of the ocular muscles in other forms of myopathy occurs but is rare. Concomitant squint    Very common Binocular fixation is not established Fixation is by the better seeing eye; the image from the other eye is suppressed, so there is no complaint of double vision. The course of the oculosympathetic pathway Horner’s syndrome  Caused by loss of sympathetic innervation to the eye. Trigeminal nerve Trigeminal Nerve (V) The trigeminal nerve and the diseases that may affect it Trigeminal nerve  The corneal reflex: Corneal stimulation  Response (mediated through the 7th cranial nerve) is to blink bilaterally   The jaw jerk:  Exaggerated in the presence of an upper motor neuron lesion above the level of the trigeminal motor nucleus in the pons bilateral. Trigeminal nerve   Lesion in the cavernous sinus affects only the ophthalmic and maxillary branches. The mandibular branch passes through the foramen oval behind the cavernous sinus.