Nystagmus, diplopia seen in 11-year-old boy
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An 11-year-old boy presented to the University of New Mexico Hospital with 6 weeks of vomiting and food intolerance as well as a 13-pound weight loss over that same period.
At the onset of these symptoms, he went to an outside hospital and was discharged without any diagnosis or medications. Subsequently, he was seen at UNMH for vomiting and was given oral ondansetron, which did not relieve his symptoms. In addition to nausea, vomiting and weight loss, the patient was experiencing 3 weeks of constant horizontal binocular diplopia, worse at distance, “eye jumping,” difficulty concentrating and headaches. He denied vision loss, pulsatile tinnitus, amaurosis or oscillopsia.
His medical history was significant for gastroschisis repaired as a newborn, gastroesophageal reflux and a fall 2 weeks prior in which he hit his right temple against a tree without loss of consciousness or vomiting at that time. He had no ocular history and followed with an optometrist every 1 to 2 years without previously noted refractive error or strabismus. Given his persistent symptoms, the patient was admitted for treatment of his dehydration related to the vomiting, as well as a workup for etiologies of his recurrent vomiting and weight loss. His primary medical team also noted that the patient had a shuffling and unsteady gait.
Examination
Upon examination at bedside, the patient’s near uncorrected visual acuity was 20/20 in both eyes. IOPs by Tono-Pen (Reichert) were 11 mm Hg and 12 mm Hg in the right and left eyes, respectively, and he was able to identify all Ishihara color plates out of each eye. The extraocular motility examination revealed a trace right abduction deficit and a –1 left abduction deficit. Additionally, there was gaze-evoked jerk nystagmus in right gaze, left gaze and upgaze. On cover-uncover testing, there was an esotropia that was evident at distance and resolved at near that did not appear worse in either right or left gaze. The visual field was full to confrontation bilaterally. Pupils were 4 mm scotopically, decreasing to 2 mm photopically bilaterally without a relative afferent pupillary defect noted in either eye.
External and anterior segment exams were unremarkable. Fundus exam revealed tortuous vasculature in both eyes. The right optic nerve did not appear pale or edematous and had a 0.15 cup-to-disc ratio. The left optic nerve appeared to have trace superior and inferior edema without pallor. The rest of the fundus exam was unremarkable.
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Constellation of findings
Given the constellation of findings of presumed bilateral abducens nerve palsies, mild left optic disc swelling, gaze-evoked nystagmus and unsteady gait, the primary concern for this patient was elevated intracranial pressure with primary pathology localizing to the cerebellum. Elevated intracranial pressure can cause stretching of the bilateral abducens nerves in Dorello’s canal, leading to bilateral sixth nerve palsies and resultant horizontal diplopia as well as optic nerve edema. Additionally, gaze-evoked nystagmus can result from medications, intoxication or lesions in the cerebellum. As the patient denied any new medications aside from ondansetron, there was concern for a space-occupying lesion of the posterior fossa/cerebellum or, less likely, a hemorrhage in the posterior fossa given the head trauma that the patient had incurred 2 weeks before symptom onset. MRI of the brain and brainstem with and without contrast was ordered for the patient.
Imaging
MRI of the brain and brainstem revealed a lobular enhancing mass of the fourth ventricle measuring 4.4 cm by 3.6 cm with resultant hydrocephalus concerning for an ependymoma or medulloblastoma (Figure 1).
Source: by Chelsea Gottschalk, MD, and Kevin Sitko, MD
Workup and management
The patient was seen by the neurosurgery team and scheduled for resection of the tumor the following morning with placement of an external ventricular drain for intracranial pressure monitoring in the postoperative period. The patient tolerated the surgery well, and the pathology of the tumor revealed a grade IV medulloblastoma, classic type. MRI of the cervical, thoracic and lumbar spine did not reveal any lesions concerning for metastases, and lumbar puncture was negative for malignant cells. The patient was started on vincristine chemotherapy as well as spinal and whole brain radiation.
On follow-up in the neuro-ophthalmology clinic 3 weeks after surgical resection of the tumor, the patient reported that he was doing well and was patching one eye to resolve his diplopia. Motility examination showed mild residual left eye abduction deficit and continued gaze-evoked nystagmus in right gaze, left gaze and upgaze. Cover-uncover testing with prisms revealed a 16 D esotropia and 6 D right hypertropia. These measurements did not change significantly in different directions of gaze. OCT of the retinal nerve fiber layer (RNFL) and dilated examination did not demonstrate any optic nerve edema (the patient was initially evaluated at bedside and was unable to get a baseline OCT RNFL for comparison). The right hypertropia was diagnosed as a skew deviation as it did not fit a pattern of a superior oblique palsy, and there was known underlying posterior fossa pathology. The patient was observed, and in follow-up 5 weeks later, the esotropia and right hypertropia were essentially unchanged. If the esotropia were from elevated intracranial pressure alone, it would be expected to resolve or improve dramatically after the treatment of the patient’s hydrocephalus, and so it is still uncertain why this remains.
Discussion
Medulloblastoma is one of the most common pediatric brain tumors after pilocytic astrocytoma. The tumors arise from the cerebellum and range from classic to anaplastic types based on their histologic characteristics. Medulloblastoma has a propensity to invade the cerebrospinal fluid and carries a survival rate around 60% to 70%. Fortunately for this patient, diagnosis was early, and there were no identified metastases on workup.
Additionally, although the patient would likely have undergone brain imaging for his diplopia, the nystagmus helped accurately localize his underlying pathology. Being able to pinpoint lesions by identifying the type of nystagmus can be helpful in ophthalmology. In broad terms, nystagmus develops when there is disruption to the vestibulo-ocular reflex, the neural integrator or the visual fixation systems. In this case of gaze-evoked nystagmus, there is dysfunction of the neural integrator, which involves the cerebellum and typically helps the eyes maintain eccentric gaze against the elastic forces of the orbit. The eyes tend to drift toward midline, and then there is a quick corrective saccade back to the eccentric gaze. The cerebellum may be affected by medications and recreational drugs, and gaze-evoked nystagmus is therefore common with alcohol use and sedatives. However, gaze-evoked nystagmus can also be indicative of general cerebellar disease. Other common localizing forms of nystagmus to be aware of include downbeat nystagmus, which indicates pathology at the cervicomedullary junction (ie, Chiari malformation), seesaw nystagmus, which indicates pathology within the parasellar region, and convergence-retraction nystagmus, which indicates pathology within the dorsal midbrain. Spending the time to observe and characterize the nystagmus can help ophthalmologists target neuroimaging and reduce delay in diagnosis.
- References:
- Diagnosis of nystagmus and saccadic intrusions. In: Leigh RJ, et al, eds. The Neurology of Eye Movements. 4th ed. Oxford; 2006.
- Dunham C. Semin Diagn Pathol. 2010;doi:10.1053/j.semdp.2010.04.003.
- Hernowo A, et al. Curr Opin Ophthalmol. 2014;doi:10.1097/ICU.0000000000000105.
- Lee AG, et al. Curr Neurol Neurosci Rep. 2006;doi:10.1007/s11910-996-0022-y.
- Pathologies in pediatric posterior fossa tumors: Medulloblastoma. In: Özek M, et al, eds. Posterior Fossa Tumors in Children. Springer; 2015:264-380.
- For more information:
- Chelsea Gottschalk, MD, and Kevin Sitko, MD, can be reached at New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.
- Edited by Allison V. Coombs, DO, MS, and Nisha S. Dhawlikar, MD, MPH. They can be reached at New England Eye Center, Tufts University School of Medicine, 800 Washington St., Box 450, Boston, MA 02111; website: www.neec.com.