Trochlear nerve sheath tumors Others:
Superior oblique myokymia
Pediatric: congenital, traumatic and idiopathic are the most frequent causes.
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
Differential diagnosis Skew deviation, a disparity in the vertical positioning of the eyes of supranuclear 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.
The vertical diplopia may be alleviated by the patching of one eye or the use of Therapy 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 Prognosis etiology than other non-selected cases.
Berlit P (1991) Isolated and combined pareses of cranial nerves III, IV, and VI. A retrospec- References 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. Neurology 43:2439-2443
Rush JA, Younge BR (1981) Paralysis of cranial nerves III, IV, and VI. Arch Ophthalmol 99:
Somatosensory evoked potentials Reflexes: masseteric, corneal reflex, EMG
Qualities Branchial motor: mastication, tensor tympani muscle, tensor veli palatini mus cle, myohyoid muscle, anterior belly of digastric muscle.
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