Neurological picture. Eight-and-a-half syndrome

A Rare Neuro-Ophthalmological Condition in a Patient with Lung Adenocarcinoma: The Eight-and-a-Half Syndrome, Case Report and Review of the Literature

The eight-and-a-half syndrome is a rare neuro-ophthalmological condition caused by a structural lesion in the dorsal portion of the pons, involving critical areas of the brainstem, i.e., medial longitudinal fasciculus (MLF), abducens nucleus, facial genu, and colliculus. It is characterized by internuclear ophthalmoplegia with horizontal gaze palsy and peripheral facial palsy. Although the syndrome is most frequently caused by vascular or demyelinating diseases, several different underlying causes might occur. Herein, we describe a case of the eight-and-a-half syndrome caused by a lung adenocarcinoma metastasis localized in the lower pontine tegmentum. Then, we review the current literature on the underlying causes of the eight-and-a-half syndrome.

Eight-and-a-half syndrome: a rare presentation

Eight-and-a-half syndrome is a rare entity characterised by conjugate horizontal gaze palsy, ipsilateral internuclear ophthalmoplegia and ipsilateral lower motor neuron type facial palsy. It is due to a lesion affecting median longitudinal fasciculus, paramedian pontine reticular formation and facial nerve fascicle on the same side at the level of pons. The diagnosis is easily missed as it needs detailed ocular movement examination. It is mainly caused due to infarction or demyelinating conditions. We are reporting an interesting case of a 54-year-old man with right-side eight-and-a-half syndrome due to acute ischaemic stroke and ST-elevation myocardial infarction of the inferior wall.

Eight-and-a-half syndrome: video evidence and updated literature review

The eight-and-a-half syndrome (EHS)-defined by the combination of a seventh cranial nerve palsy and an ipsilateral one-and-a-half syndrome-is a rare brainstem syndrome, which localises to the caudal tegmental region of the pons. We present a case of the EHS secondary to an inflammatory lesion on a previously healthy 26-year-old woman, with a literature review emphasising the relevance of aetiological assessment.

Eight-and-a-half syndrome: a rare potentially life-threatening disease

Purpose: To report a case of eight-and-a-half syndrome presenting with a conjugate horizontal gaze palsy, an ipsilateral internuclear ophthalmoplegia, and an ipsilateral lower motor neuron-like facial palsy.

Methods: A 56-year-old male who came in for limitation of extraocular muscle motion – wherein the only remaining movement is abduction of the left eye – and right-sided facial weakness. Magnetic resonance imaging revealed a well-defined lesion resembling a cavernoma, at the level of the ponto-medullary junction.

Results: Eight-and-a-half syndrome results from a lesion affecting the paramedian pontine reticular formation, the median longitudinal fasciculus, and the facial nerve fascicle on one side. In this case, a cavernoma at the level of the ponto-medullary junction was compressing the important pontine structures.

Conclusion: Although eight-and-a-half syndrome is most commonly caused by an infarction or demyelination, in rare instances, a space-occupying lesion at the level of the pons can be the etiology. It is of utmost importance to recognize the features of this disease entity to be able to exhaust the proper diagnostic exams, localize the lesion and determine the proper treatment regimen catered to each patient.

Pontine haemorrhage disguised as Bell's palsy

Isolated facial nerve palsy is a common presentation of Bell's palsy, but rarely seen in pontine lesions. The patient being reported is a middle-aged man who developed isolated facial nerve palsy and was initially treated as Bell's palsy. However, on MRI of the brain, he was found to have pontine haemorrhage. He was managed conservatively and improved. Pontine haemorrhage as an aetiology for isolated facial nerve palsy is a rare scenario, which often goes misdiagnosed and treated as Bell's palsy.

Eight-and-a-half syndrome caused by a pontine haemorrhage: a case report and review of the literature

BACKGROUND

Eight-and-a-half syndrome is caused by a lesion in the dorsal tegmentum of the caudal pons involving parapontine reticular formation and median longitudinal fasciculus, as well as the nucleus and/or the fasciculus of the facial nerve. It is characterized by one-and-a-half syndrome and an ipsilateral cranial nerve VII palsy. Also, many variants of eight-and-a-half syndrome have been described, including nine syndrome, thirteen-and-a-half syndrome and fifteen-and-a-half syndrome.

METHODS

We describe a case of a 49-year-old man who presented with eight-and-a-half syndrome combined with contralateral hemiparesis. We reviewed the literature describing the related spectrum of eight-and-a-half syndrome associated with various etiologies.

RESULTS

Brain computed tomography scan revealed a hyperdensity located in the left paramedian aspect of the dorsal pons. T2-weighted magnetic resonance imaging at the 11-month follow-up showed hyperintensity and enlargement of the inferior olivary nuclei, which were compatible with a diagnosis of hypertrophic olivary degeneration. In light of our observations and cases reported in the literature, we categorize the spectrum of eight-and-a-half syndrome into three types, namely classic eight-and-a-half syndrome, eight-and-a-half syndrome variants and eight-and-a-half plus syndrome. Besides, the clinical feature and outcome of the three types are discussed in this article.

CONCLUSIONS

Recognition of the spectrum of eight-and-a-half syndrome allows precise anatomic localization of the lesion to pontine tegmentum region.

One-and-a-half syndrome with its spectrum disorders

One-and-a-half syndrome is a syndrome characterized by horizontal movement disorders of the eyeballs, which was first reported and named by Fisher in 1967. It presents a combination of ipsilateral conjugate horizontal gaze palsy (one) and ipsilateral internuclear ophthalmoplegia (INO) (a half). On the basis of the one-and-a-half syndrome, there are a series of related rare syndromes called the one-and-a-half syndrome spectrum disorders. This article reviews rare cases of one-and-a-half syndrome spectrum disorder, describes the clinical and pathological features of different syndromes, and summarizes their nomenclature.