‘Twenty syndrome’ in neuromyelitis optica spectrum disorder

Correspondence to Dr Souvik Dubey; [email protected]

Background

In 1967, Fisher was the first person to report a peculiar horizontal movement disorder of eyeballs where there was combination of ipsilateral conjugate horizontal gaze restriction (one) and ipsilateral internuclear ophthalmoplegia (INO) (a half), thus numerically being one-and-a-half syndrome.¹ Following that seminal neuro-ophthalmological observation, various numerical neuro-ophthalmological syndromes affecting extraocular movements and cranial nerves have been described, such as eight-and-a-half syndrome, nine syndrome, thirteen-and-a-half syndrome, fifteen-and-a-half syndrome, sixteen syndrome, sixteen-and-a-half syndrome, twenty-and-a-half syndrome and twenty-four syndrome collectively known as ‘one-and-a-half syndrome with its spectrum disorders’.^2–5 Lesions involving the combination of either medial longitudinal fasciculus (MLF) plus abducens nerve nucleus or involvement of MLF plus paramedian pontine reticular formation (PPRF) can cause one-and-a-half syndrome.⁶ As nucleus of abducens is located in close proximity of facial, vestibulocochlear and trigeminal nerve nucleus, they are frequently affected by the same pathologic process causing one-and-a-half spectrum disorders.² The involvement of a bilateral facial nerve with one-and-a-half syndrome was termed as fifteen-and-a-half syndrome by Bae and Song.⁷ Unlike INO (which can be caused by vascular, demyelination and space occupying lesions), till date only cerebrovascular diseases involving bilateral pontine tegmentum have been described as the cause of fifteen-and-a-half syndrome.^7–9

Here, a case of ‘twenty syndrome’, characterised by one-and-a-half syndrome with facial diplegia, bilateral optic neuritis and left ataxic haemiparesis (1¹/₂+7+7+2+2+¹/₂=20), is being reported for the first time ever in a patient with demyelinating lesions in bilateral pontine tegmentum and optic nerves, ultimately diagnosed as neuromyelitis optica spectrum disorder (NMOSD).

Case presentation

A 30-year-old married woman of Asian-Indian ancestry presented with sudden-onset diminution of vision (DOV) in bilateral eyes progressing within 6 hours. She reported of colours appearing less luminous, dirty and pale, eyeball misalignment and inability to move the eyeballs according to her will, painful eye movement on effort for same duration. She also had weakness of the left side of the body, gait unsteadiness and slurring of speech since she woke up from sleep 8 hours back with. On detailed inquiry, she revealed that all the symptoms started with severe hiccups and multiple episodes of vomiting since the previous evening. There was no history of trauma, fever, loss of consciousness,...