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Atrophy of the superior oblique muscle
  1. U-M Sheerin1,
  2. A Trip2,
  3. F Schon3,4
  1. 1
    Specialist Registrar in Clinical Genetics
  2. 2
    Specialist Registrar in Neurology
  3. 3
    Consultant Neurologist
  4. 4
    Department of Neurology, St George’s Hospital, London, UK
  1. Dr F Schon, Department of Neurology, Atkinson Morley Wing, St George’s Hospital, Blackshaw Road, London SW17 0QT, UK; frederick.schon{at}mayday.nhs.uk

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A previously healthy 59-year-old woman presented five years ago with intermittent vertical double vision which soon became continuous, without any other relevant associated history. She noticed the double vision disappeared on tilting her head downwards and to the right (fig 1A). Photographs from when she was younger (fig 1B) confirmed that her head had previously been in a normal position. Neurological examination revealed a resting head tilt to the right, and eye movement examination revealed failure of depression of the adducted left eye consistent with a left superior oblique palsy. Tilting the head to the left (the Bielschowsky head tilt test) exacerbated the vertical separation of the images. She had normal routine blood tests, acetylcholine receptor antibody, CSF examination including oligoclonal bands, ECG and chest x ray. MRI of the brain was normal but orbital MRI showed almost complete atrophy of the left superior oblique muscle (fig 2). Both her clinical condition and MR scan have remained unchanged over the last five years. No cause for her acquired fourth nerve palsy has emerged.

Figure 1 (A) Head tilt currently. (B) Normal head position in adolescence. Informed consent was obtained for publication of this figure.
Figure 2 (A) T1 and (B) T2 coronal MRI scans demonstrating atrophy of the left superior muscle oblique (arrows).

COMMENT

Head tilt is a sign in patients who may or may not have noticed that by slanting their head they can reduce their double vision, usually in cases of unilateral fourth nerve palsy as here (of course head tilt may also be seen in spasmodic torticollis too). The patients complain of vertical diplopia maximal on down gaze, usually with torsional separation of the images, and looking to the side opposite the lesion; and they usually have a compensatory head tilt to the opposite side (that is, with the normal eye lower than the affected eye).

Isolated superior oblique palsy may be caused by a number of different problems, most commonly an isolated trochlear nerve lesion which is the least common of the three cranial nerve lesions causing double vision, accounting for only 15% in the largest series of 4373 acquired cases.1 Approximately one third of cases of isolated trochlear nerve lesions are idiopathic as in our case, one third are the result of head injury, and the remainder a result of a range of conditions including vascular, neoplastic and aneurysmal lesions.

A less familiar cause of head tilt is in patients who compensate, more often unconsciously than consciously, for subjective sloping of their visual world associated with brainstem lesions resulting in skew deviation where one eye is above the other on the horizontal axis. Until recently this was felt to be a rare condition resulting from a variety of brainstem lesions with little or no localising significance. Currently however there is increasing evidence that it is relatively common and results from abnormal vestibular inputs to the ocular motor nerve nuclei, usually due to abnormalities involving the central otolithic pathways (inputs from the utricle).2

Acknowledgments

This article was reviewed by Christian Lueck, Canberra, Australia.

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