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Diagnosis and management of IV cranial nerve palsy Ali Yagan explores diagnosis and treatment of fourth nerve palsy, also known as trochlear nerve palsy.

Aetiology: “It is important to have a period of stable measurements Trochlear nerve palsy can be divided into acute or congenital. Congenital trochlear of at least six months before embarking on surgery.” nerve palsy is usually noted in childhood with development of abnormal head posture. Various pathologies can lead tests for autoimmune antibodies, ACh-R Ito procedure, Knapp class I can be to acute IV nerve palsy, most commonly antibodies are done if felt necessary. addressed by ipsilateral IO recession, class trauma. Other causes include vascular II can be addressed by ipsilateral SO tuck, (ischaemic), inflammatory (demyelination), Management options: class III can benefit from either options neoplastic and aneurysms. It is important to fully investigate the and class IV and V might need also a contralateral inferior rectus recession. It is Signs and symptoms: patient and treat any pathology if possible or control risk factors for vascular disease. important to counsel the patient about the It is very important to differentiate acute IV Symptomatic treatment to address diplopia possibility of unmasking a bilateral IV palsy cranial nerve (CN) palsy from longstanding includes patching, prisms and surgery. following surgery on one eye then needing but decompensating one. Patients usually further surgical intervention. Adjustable present with sudden onset, intermittent or sutures could be utilised in adults’ surgery. constant vertical diplopia. Full orthoptic Non-surgical options: These include patching one eye or using assessment is essential to confirm the Complications: condition. The assessment will show that Fresnel prisms in order to avoid diplopia, It is important to avoid over corrections the affected eye is hypertropic and this it is also important to tell patients to avoid by staging the surgery or using adjustable hypertropia increases on contralateral gaze driving and inform the DVLA about their sutures. Other specific complications and on ipsilateral head tilt (3 step test). It diplopia. include inducing a Brown syndrome is also important to obtain a Hess chart following SO tuck and it is important to as well as assessing the patient on the Knapp classification: counsel patients regarding this possibility. synoptophor looking for subjective torsion. This is a useful way of classifying IV nerve IR muscle surgery can induce lower lid Fundus photography looking at the position palsy as it helps planning surgical treatment malposition. of the fovea relative to the optic nerve head options. is a way of detecting objective torsion. Class I: greatest hypertropia in ipsilateral References inferior oblique (contralateral up) 1. Ansons A, Davis H. Diagnosis and management of ocular motility disorders. 4th edition. Wiley & Sons Ltd: Oxford, field Common features of longstanding UK; 2014. IV nerve palsy: Class II: greatest hypertropia in ipsilateral 2. Miller NR, Newman NJ. Walsh & Hoyt Clinical Neuro 1. Extended vertical fusion range superior oblique (contralateral Ophthalmology. The essentials. 2nd edition. Lippincott 2. Lack of subjective torsion down) field Williams & Wilkins: Philadelphia USA; 2008. 3. Development of muscle sequelae on Hess Class III: greatest hypertropia in entire chart contralateral field 4. Longstanding head tilt to the Class IV: greatest hypertropia in entire SECTION EDITOR contralateral side. contralateral field and across the lower field Common features of bilateral IV Class V: greatest hypertropia across lower cranial nerve palsy: field 1. Reversal of the vertical deviation on side Class VI: bilateral IV palsy gazes Class VII: traumatic paresis combined with 2. Torsion of more than 10 prism dioptres in Brown’s syndrome. primary gaze 3. V pattern Surgical options: 4. Chin up position instead of head tilt. It is important to have a period of stable Ali Yagan, measurements of at least six months before Consultant Ophthalmic Surgeon, Neuro- Investigations: embarking on surgery. The surgical option Ophthalmology and Adult Strabismus Fellowship, Once confirmed as acute onset, several depends on the angle of deviation in primary Manchester Royal Eye Hospital, Manchester, UK. investigations are recommended including position, area of maximum deviation and E: [email protected] neuro imaging (MRI), blood tests such as presence of torsion. ESR, CRP, FBC, glucose, lipids, U&Es. Other Torsion can be corrected by the Harada

eye news | OCTOBER/NOVEMBER 2017 | VOL 24 NO 3 | www.eyenews.uk.com