Isolated Ischaemic Bilateral Internuclear Ophthalmoplegia with Rapid Recovery

Han Ni

Background

Internuclear ophthalmoplegia (INO) is due to a lesion in the medial longitudinal fasciculus (MLF) containing internuclear neurons from the abducens nucleus in the pons to the contralateral oculomotor nucleus in the midbrain. Characteristically, INO manifests as adduction deficit of ipsilateral eye on attempted lateral gaze and nystagmus of the abducting eye.

Case Presentation

A 57-year-old man presented with sudden onset of diplopia associated with abnormal bilateral horizontal eye movements of one day duration. Neurological examination revealed impaired adduction of both eyes on lateral gaze and preserved abduction of both eyes with abducting nystagmus. In the primary position, right eye was in the midline but the left eye was mildly exotropic. Upward and downward gaze were preserved. Motor, sensory and other neurological examinations were unremarkable. On the second day of admission, adduction of both eyes improved significantly, however, double vision and nystagmus remained. On the third day, he had near normal eye movements with no diplopia. Non contrast enhanced CT brain on the day of admission revealed multifocal acute cerebral infarction areas at bilateral corona radiata, bilateral basal ganglia and left external capsule. Due to resource limitations, MRI brain was not available immediately. While waiting for scheduled MRI months later, the patient was lost to follow-up.

Fig. 1: Looking to the left (A); Looking to the right (B)

Discussion

Any lesion that interrupts MLF presents with INO; multiple sclerosis and ischaemic stroke being the most frequent aetiologies. Bilateral INO is more common than unilateral INO. The commonest cause of bilateral INO is multiple sclerosis, reported in 40.9% of 22 cases in one study¹ and 34% of 410 cases in another study². Infarction in the anteromedial midbrain and pons is also a well-known cause of INO accounting for 27.2% in 22 cases1 and 38% in 410 cases². INO caused by MS is seen in younger patients less than 45 years of age whereas INO due to stroke occurs in patients 45 years or older with vascular risk factors¹. However, age alone is insufficient to determine ischemic or demyelination as the etiology of INO. Other unusual causes of INO include trauma, herniation, infections, tumours, surgery or procedures, brainstem haemorrhage and vasulitis².

INO of ischemic origin is usually unilateral in middle aged and elderly adults. Brainstem infarction involving either midbrain or pons is the commonest cause of unilateral INO. However, there have been reported cases of bilateral INO arising from focal paramedian midbrain tegmentum infarction and unilateral pontine infarction. A study of autopsy cases demonstrated that the terminal portion of a pontine tegmental paramedian artery may divide into two branches to supply MLF on both sides. Thus, occlusion of a single perforating paramedian tegmental pontine artery branch of the basilar artery could lead to bilateral INO³.

Our patient presented with isolated bilateral INO and recovered within three days. Isolated INO caused by brain stem stroke has faster improvement than INO associated with mild neurological deficits⁴. Transient bilateral INO lasting 5 minutes each for two episodes as “pontine warning syndrome” has also been reported5. With vascular risk factors of smoking, hypertension and hypercholesterolemia, our patient’s transient bilateral INO was clinically most likely to be of ischaemic origin though the imaging results were limited.

Acknowledgement

We would like to express our utmost gratitude to the patient and his family members for giving consent for this communication. In addition, we gratefully acknowledge Newcastle University Medicine Malaysia for providing necessary support and resources that made the preparation of the manuscript possible.

Conflict of Interest

None declared.

References :

1. Bolan˜os I, Lozano D, Cantu´ C. (2004) Internuclear ophthalmoplegia: causes and long-term follow-up in 65 patients. Acta Neurol Scand;110:161–5.
2. Keane JR. (2005) Internuclear Ophthalmoplegia: Unusual Causes in 114 of 410 Patients. Arch Neurol;62:714-717.
3. Fisher CM. (2004) Neuroanatomic evidence to explain why bilateral internuclear ophthalmoplegia may result from occlusion of a unilateral pontine branch artery. J Neuroophthalmol; 24:39–41.
4. Kim JS. (2004) Internuclear ophthalmoplegia as an isolated or predominant symptom of brainstem infarction. Neurology;62:1491–6.
5. Saposnik G, Noel de Tilly L, (2008) Caplan LR: Pontine warning syndrome. Arch Neurol; 65(10):1375-7.

Author Information

Han Ni

Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom, Newcastle University Medicine Malaysia (NUMed), 1, Jalan Sarjana 1, Kota Ilmu, Educity@Iskandar, 79200 Iskandar Puteri, Johor, Malaysia.