Eye movement abnormalities always clench the eyes of a neurologist to reach an interesting diagnosis most of the time in children. The common etiologies affecting the complex brainstem pathways and frontal eye field controlling conjugate eye movement are childhood stroke (pontine infarct), demyelinating disorders, mass lesions, trauma and metabolic or mitochondrial diseases. Horizontal eye movements are conducted by the medial rectus and the lateral rectus muscles. Medial rectus is innervated by oculomotor nerve (cranial nerve III) and the lateral rectus is innervated by abducens nerve (cranial nerve VI) respectively. The oculomotor and the abducens nuclei are interconnected by medial longitudinal fasciculus (MLF). The disorders of horizontal eye movement that are caused by brainstem lesions are classified into three groups: lateral gaze palsy, internuclear ophthalmoplegia, and one-and-a-half syndrome. In the present study, three interesting cases with gaze palsy have been taken into account. Case 1 is an 8-year-old boy presented with left sided hemiparesis and right sided gaze palsy with loss of adduction in right eye (One–and-half syndrome). MRI showed large areas of increased T2W signal intensity both in subcortical white matter and brain stem (involving abducens nucleus, PPRF and ipsilateral MLF). Case 2 is also of a 10-year-old boy, diagnosed to be a case of Clinically Isolated Syndrome (CIS) with ataxia and ophthalmoplegia. MRI showed areas of sub-cortical demyelination in both fronto-parietal region (right side more involved than left) with brain stem and cerebellum unaffected. Case 3 is about an 18-month-old boy presented with complete ophthalmoplegia (Inability to move both the eyes with absent conjugate movement in all directions) and delayed developmental milestones. Lactate was raised in venous blood and MRI showed necrosis in basal ganglia (thalami) and brain stem, with MR spectroscopy showed double lactate peak consistent with Leigh disease (mitochondrial encephalomyopathy).
Jayitri Mazumdar, Sumita Pal, Gautam De and Kartik Chandra Ghosh