Purpose: To describe a case of Homonymous hemianopia after implantation of deep brain stimulation for the treatment of Parkinson’s disease.
 
Study Design: Case report

Methods: Review of patient charts including history, clinical notes and relevant investigations.

Results: 41 year old female with a history of Parkinson’s disease was admitted to the hospital for influenza-like illness. During her stay, she had a headache exacerbation with transient tunnel vision prompting a lumbar puncture (LP) and a CT head. The LP yielded an opening pressure of 42 cmH20 while the CT did not show any acute abnormalities. Her past medical history was significant for juvenile onset Parkinson’s disease resulting in severe autonomic dysfunction such that she had severe gastroparesis requiring total parenteral nutrition, and recurrent UTIs secondary to neurogenic bladder.  In 2016, she underwent implantation of bilateral deep brain stimulation electrodes in the subthalamic nucleus for the treatment of her Parkinson’s disease. Her medications included lorazepam, sinemet, mirtazapine, lamotrigine, lansoprazole, and morphine suppositories.

The Neuro-Ophthalmogical examination was essentially normal and CT scan did not show any evidence of an acute intracranial process. No cause could be identified for the high intracranial pressure and diagnosis of idiopathic intracranial hypertension (IIH) was given. In regards to localization, it should be noted that although the ICP was high, visual field damage from IIH is usually seen in the optic nerve head (2), whereas no pathologic changes were seen in our patient. Moving onto the retro chiasmal pathway, the lesion is unlikely to exist in the optic tract as there was no evidence of bowtie atrophy and the patient did not have a RAPD (3). Furthermore, an MRI did not show any evidence of strokes or intracranial masses, that could have caused the right homonymous field constriction. The radiologist did note a pattern of encephalomalacia along the course of the electrodes. This may support our speculation that the placement of electrodes, either through ischemic or mechanical damage, resulted in damage to the region near the left lateral geniculate nucleus. 

Conclusion: To our knowledge this is the first reported case of homonymous hemianopia associated with Deep Brain Stimulation. Neurosurgical procedures and trauma have been previously reported as causes for homonymous hemianopsia. Therefore, it is likely that the implantation of the deep brain stimulation device, either through trauma or ischemic changes, resulted in the homonymous hemianopsia.

Homonymous hemianopsia after treatment with deep brain stimulation

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