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Man experiences sudden onset binocular diplopia
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A 54-year-old man was transported to the emergency room from a rehabilitation facility with sudden onset double vision, left-sided weakness and right-sided facial droop. The patient had been recovering after a recent hospitalization for subacute endocarditis and a cerebellar cerebrovascular accident when he noticed sudden onset horizontal double vision that was present in all fields of gaze, inability to close his right eye and left-sided weakness.
His medical history was significant for the aforementioned hospital admission, hypertension, IV drug abuse, hepatitis C and two aortic valve replacements. Also of note, 2 weeks before his presentation he was diagnosed with HSV keratitis in the left eye. His medications included aspirin, ceftriaxone, gentamicin, citalopram, nabumetone, omeprazole, tramadol, cyclopentolate and valacyclovir.
The patient’s external exam showed right-sided facial droop with intact corneal and facial sensation on the right. Uncorrected visual acuity was 20/40-2 in the right eye and 20/50+2 in the left eye with no improvement on pinhole. Pupils were symmetric in size, and no afferent defect was present. Although they were sluggish, they did react to light and dark. Color vision and confrontational fields were full in both eyes.
Figure 1. 1: Neutral gaze with left exotropia. 2: Right gaze with limited abduction in the right eye and adduction in the left eye. 3: Left gaze with limited adduction in the right eye and intact abduction in the left eye. 4: Intact upgaze with left exotropia. 5: Intact downgaze with left exotropia.
Images: Hansen BA, Athappilly G
Figure 2. T2 MRI with FLAIR. Note acute lacunar infarct in the pontine tegmentum in the vicinity of the medial longitudinal fasciculus with inferior extension seen in the lower images. Also note areas of prior cerebellar infarction.
Extraocular movements are shown in Figure 1. The patient had a left exotropia on primary gaze. In right gaze, there was limited abduction in the right eye and adduction in the left eye. In left gaze, there was limited adduction in the right eye but normal abduction in the left eye. Superior and inferior gaze was overall unremarkable without a perceptible skew deviation. The right eye anterior exam was significant for lagophthalmos, conjunctival injection and exposure keratitis. In the left eye there was 1+ injection, an irregular corneal epithelium without a defect and linear dendritiform anterior stromal scarring but no active infiltrate. The posterior exam was unremarkable.
An MRI showed an acute infarct in the pontine tegmentum in the vicinity of the medial longitudinal fasciculus (Figure 2).
A transesophageal echocardiogram done on admission showed large vegetations on the patient’s aortic valve homograft as well as a perivalvular abscess with valve dehiscence. Blood cultures grew Streptococcus viridans.
What is your diagnosis?
Sudden onset binocular diplopia
The patient’s ocular misalignment was consistent with “one-and-a-half syndrome.” This disorder is characterized by an ipsilateral conjugate horizontal gaze palsy and ipsilateral internuclear ophthalmoplegia due to involvement of the abducens nucleus and ipsilateral medial longitudinal fasciculus. Initially these patients may show a contralateral paralytic pontine exotropia.
Due to his additional findings of right-sided fascicular facial nerve palsy and left-sided weakness from involvement of the corticospinal tracts and medial lemniscus, the term “eight-and-a-half syndrome” or the recently described “nine syndrome” more accurately encompasses of all his symptoms.
The differential diagnosis for multi-cranial neuropathies is rather broad and includes demyelinating disease (Guillain Barre-Miller Fisher variant, multiple sclerosis), metabolic causes (thyroid, Wilson’s disease), infectious causes (botulism, cephalic tetanus, encephalitis/meningitis), inflammatory causes (neurosarcoid, Behçet’s), vascular causes (basilar artery aneurysm, arteriovenous malformation), ischemic/embolic causes (acute pontine or mesodiencephalic lesions), myasthenia gravis and trauma. Additional ischemic pontine syndromes are listed in Table 1.
Discussion
The features of one-and-a-half syndrome were first characterized in 1967 by the neurologist C. Miller Fisher. The prevalence has not been reported, but it is a rare syndrome characterized by an ipsilateral conjugate gaze palsy (“one”) and an ipsilateral internuclear ophthalmoplegia (“half”). The findings are secondary to a unilateral disruption of the paramedian pontine reticular formation (or alternatively the ipsilateral abducens nucleus) and the already decussated medial longitudinal fasciculus (Figure 3). These lesions result in a lateral gaze palsy (toward the side of the lesion) and decreased adduction of the ipsilateral eye. There is often abducting nystagmus of the contralateral eye and initially contralateral paralytic pontine exotropia. The most common presenting symptoms for patients with one-and-a-half syndrome include diplopia, blurred vision and oscillopsia.
Figure 3. One-and-a-half syndrome. Disruption of paramedian pontine reticular formation and/or abducens nucleus plus the decussated medial longitudinal fasciculus.
Figure 4. Eight-and-a-half syndrome. One-and-a-half syndrome plus disruption of facial nerve colliculi as it courses around the abducens nucleus.
Figure 5. Nine syndrome. Eight-and-a-half syndrome plus disruption of the medial lemniscus and the corticospinal tract.
In a review by Wall et al, the etiologies of one-and-a-half syndrome were reported in a 49 patients. Of these, 16 (32.6%) were due to brainstem infarct, 16 (32.6%) due to multiple sclerosis and eight (16.3%) from pontine hemorrhage. Other etiologies included pontine glioma, cerebellar astrocytoma, metastatic carcinoma and an ependymoma of the fourth ventricle. More recently, a case by Tsai et al described a 48-year-old patient with native valve endocarditis who had a pontine embolic event with resultant one-and-a-half syndrome. Similarly, the presumptive etiology for our patient, given his history and echo findings, is an embolic event related to his homograft endocarditis.
An even more rare entity is that of eight-and-a-half syndrome. This syndrome was first described by Eggenberger in 1998. It is characterized by a one-and-a half syndrome plus disruption of the ipsilateral facial nerve colliculi as they course around the abducens nucleus (Figure 4). In 2013, Rosini et al suggested a new characterization of eight-and-a-half syndrome plus contralateral hemiparesis and hemihypesthesia, described as the nine syndrome (Figure 5). In their case, they described a 71-year-old vasculopathic patient with signs, symptoms and MRI evidence of eight-and-a-half syndrome plus contralateral hemiparesis and hemihypesthesia. The pontine lesion was thought to extend ventrally into the ipsilateral medial lemniscus (controlling contralateral touch, vibration and proprioception) and corticospinal tract (contralateral motor function). Our patient’s presenting symptoms and imaging aligned with this newly characterized syndrome.
Treatments are controversial, as the symptoms often spontaneously resolve with time. When no improvement occurs, treatment modalities consist of botulinum exotoxin A injections (both retrobulbar and intramuscular), oral therapy (baclofen, benzodiazepines, propranolol, scopolamine), patching or prisms. Most importantly, the etiology of the disorder needs to be explored and treated accordingly.
Follow-up
Our patient was followed closely by neurology, infectious disease and cardiothoracic surgery. It was determined by two different academic institutions that, although his multiple embolic events were likely from his valvular vegetations, he was not a surgical candidate. He was continued on IV ceftriaxone for a total of 8 weeks and given aspirin for antiplatelet therapy. He was discharged again to a rehab facility with plans for outpatient ophthalmologic follow-up in 1 month.