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42 Regeneration after trauma: May be aberrant and posttraumatic innervation may cause erroneous innerva-tion of adjacent muscles. Others causes: Migraine: Ophthalmoplegic migraine Pediatric oculomotor lesions: Congenital, traumatic, and inflammatory causes are most common. Diagnosis Differential diagnosis Therapy Prognosis References Fasting glucose Imaging, especially to exclude aneurysm Botulism (pupils) Brainstem disorders and Miller Fisher Syndrome Congenital lesions Hereditary conditions Myopathy – chronic progressive external ophthalmoplegia Myasthenia Gravis Long duration of defects may require prism therapy or strabismus surgery. Depends on the treatment of the underlying pathology. If the lesion is of vascular etiology, resolution occurs usually within 4–6 months. Jacobson DM (2001) Relative pupil-sparing third nerve palsy: etiology and clinical vari-ables predictive of a mass. Neurology 56: 797–798 Keane JR (1983) Aneurysms and third nerve palsies. Ann Neurol 14: 696–697 Kissel JR, Burde RM, Klingele TG, et al (1983) Pupil sparing oculomotor palsies with internal carotid-posterior communicating aneurysms. Ann Neurol 13: 149–154 Richards BW, Jones FRI, Young BR (1992) Causes and prognosis in 4278 cases of paralysis of oculomotor, trochlear and abducens cranial nerve. Am J Ophthalmol 113: 489–496 This is trial version www.adultpdf.com 43 Trochlear nerve Genetic testing NCV/EMG Laboratory Imaging Biopsy + + Somatic motor to the superior oblique muscle. Qualities The trochlear nucleus is located in the tegmentum of the midbrain at the inferior colliculus, near the midline and ventral to the aqueduct. Axons leave the nucleus and course dorsally around the aqueduct and decussate within the superior medullary velum (thus, each superior oblique muscle is innervated by the contralateral trochlear nucleus). The axons exit from the midbrain on its dorsal surface and travel around the cerebral peduncle, emerging between the posterior cerebral and superior cerebellar arteries with the oculomotor nerve. The trochlear nerve pierces the dura at the angle between the free and attached borders of the tentorium cerebelli. It then enters the lateral wall of the cavern-ous sinus, along with the ophthalmic nerve (V1), CNIII, and sometimes the maxillary nerve (V2). It enters the superior orbital fissure, passes above the tendinous ring, crossing medially along the roof of the orbit, then diagonally across the levator palpebrae. The nerve breaks into three or more branches as it enters the superior oblique muscle. Lesion sites include the midbrain, subarachnoid space, cavernous sinus, supe-rior orbital fissure, or orbit. Patients experience vertical diplopia that increases when the gaze is directed downwards and medially. The affected eye is sometimes extorted (although this may not be apparent to the observer) and exhibits poor depression during adduction. Hypertropia may occur if the weakness is severe. Isolated lesion of the trochlear nerve is rare, although it is the most common cause of vertical diplopia. More often trochlear nerve dysfunction is observed in association with lesions of CNIII and CNVI. Metabolic: Diabetes Vascular: Hypertension Subarachnoid hemorrhage Anatomy Topographical localization of lesion Symptoms Signs Pathogenesis This is trial version www.adultpdf.com 44 Uncertain: microvascular infarction Vascular arteriosclerosis, diabetes (painless diplopia) Infection: Mastoiditis Meningitis Inflammatory: Ophthalmoplegia or diplopia associated with giant cell arteritis Compression: Cavernous sinus, orbital fissure lesions Inflammatory aneurysms ( posterior cerebral artery, anterior superior cerebellar artery) Trauma: Head trauma causing compression at the tentorial edge Lumbar puncture or spinal anesthesia Surgery The trochlear nerve is the most commonly injured cranial nerve in head trauma. Neoplastic: Carcinomatous meningitis Cerebellar hemangioblastoma Ependymoma Meningioma Metastasis Neurilemmoma Pineal tumors Trochlear nerve sheath tumors Others: Superior oblique myokymia Pediatric: congenital, traumatic and idiopathic are the most frequent causes. Diagnosis Differential diagnosis Diagnosis can be facilitated by the Bielschowsky test: 1. Hypertropia of the affected eye 2. Diplopia is exacerbated when the affected eye is turned nasally 3. Diplopia is exacerbated by gazing downward 4. Diplopia is improved by tilting the head away from the affected eye Also, when viewing a horizontal line, the patient sees two lines. The lower line is tilted and comes closest to the upper line on the side towards to the affected eye. Subtle diagnosis: “Cross over” or Maddox rod techniques Skew deviation, a disparity in the vertical positioning of the eyes of supra-nuclear origin, can mimic trochlear palsy. Myasthenia gravis, disorders of the extraocular muscles, thyroid disease, and oculomotor palsy that affects the superior rectus can also cause similar effects. This is trial version www.adultpdf.com 45 The vertical diplopia may be alleviated by the patching of one eye or the use of prisms. Surgery could be indicated to remove compression or repair trauma. The recovery rate over 6 months was observed to be higher in cases of diabetic etiology than other non-selected cases. Berlit P (1991) Isolated and combined pareses of cranial nerves III, IV, and VI. A retrospec-tive study of 412 patients. J Neurol Sci 103: 10–15 Jacobson DM, Marshfield DI, Moster ML, et al (2000) Isolated trochlear nerve palsy in patients with multiple sclerosis. Neurology 55: 321–322 Keane JR (1993) Fourth nerve palsy: historical review and study of 215 inpatients. Neurol-ogy 43: 2439–2443 Rush JA, Younge BR (1981) Paralysis of cranial nerves III, IV, and VI. Arch Ophthalmol 99: 76–79 Therapy Prognosis References This is trial version www.adultpdf.com 46 Trigeminal nerve Genetic testing NCV/EMG Laboratory Imaging Biopsy + + ++ Somatosensory evoked potentials Reflexes: masseteric, corneal reflex, EMG Fig. 4. a 1 Mandibular nerve, 2 Inferior alveolar nerve, 3 Men-tal nerve. b 1 Temporal muscle, 2 Masseteric muscle, 3 ptery-goid muscles. ... - tailieumienphi.vn
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