Cerebral arteriovenous malformation presenting as visual deterioration in a child

Diagnosing and managing functional visual complications after brain injury

BACKGROUND

Brain injury caused by an arteriovenous malformation (AVM) hemorrhage is an uncommon occurrence in a teenager. An AVM is a congenital anomaly of unknown etiology, often described as a tangle of arteries and veins that may vary in length and width leading to a loss of capillary bed. The vessels can break down with time and cause hemorrhage or aneurysm. Hemorrhage occurs in a significant number of patients with AVM. Intracranial hemorrhage causes brain injury, which can lead to systemic and ocular complications, neurologic deficits, and death.

CASE REPORT

A 15-year-old girl presented to our clinic with a chief complaint of horizontal diplopia while reading, lasting from seconds to 5 minutes. Nine months before the examination she had a ruptured cerebral AVM, then surgery to control the bleeding. She spent 6 weeks in a coma after surgery and woke up a hemiplegic. There were no visual problems before the bleeding. Our evaluation showed accommodative insufficiency, oculomotor dysfunction, dry eye syndrome, and a right beating latent nystagmus in both eyes. Perceptual testing showed a severe visual sequential memory deficit. The patient was given a reading prescription to aid with accommodation and was to use artificial tears and lacrilube ointment. At the follow-up examination, she reported increased efficiency and fewer episodes of diplopia while reading with bifocals and fewer dry eye symptoms since using the artificial tears.

CONCLUSIONS

After a brain injury, a young adult can present with perceptual and visual efficiency problems as well as nystagmus. It is important to test all areas that may be affected by this type of event and to investigate all complaints thoroughly with continued follow-up care. A latent nystagmus was discovered during thorough near point testing. The visual perceptual testing helped to confirm the visual sequential memory deficit, which may otherwise have been overlooked. It is believed that the diplopic complaint and poor oculomotor skills were directly related to the newly acquired nystagmus.

Steal affecting the central nervous system

Steal is a pathophysiological process in which increased blood flow through a low-resistance vascular bed is sufficient to divert flow away from a region of the central nervous system. Three disease states in which steal may cause neurological deficits due to central nervous system ischemia are reviewed. Subclavian steal occurs when stenosis of the subclavian artery proximal to the vertebral origin causes retrograde flow in the left vertebral artery. Patients with anatomic subclavian steal usually do not develop neurological symptoms but may rarely present with posterior circulation ischemia. Arteriovenous malformations alter cerebral blood flow patterns and regional perfusion pressure. It has been hypothesized that cerebral arteriovenous malformations may cause neurological deficits due to steal and that these deficits may be cured with arteriovenous malformation treatment. Intra-arterial pressure measurements and transcranial velocity studies show regional hemodynamic alterations. However, these changes have not been correlated with presenting symptoms. Evidence from single-photon emission computed tomography does suggest a relationship between regional hypoperfusion and neurological deficits. Coarctation of the aorta may divert flow from the spinal cord circulation through intercostal arteries distal to the stenosis. This is a possible but unproven mechanism of myelopathology. Steal syndromes may be amenable to treatment by open surgical or endovascular approaches. Experimental studies of the pathophysiology of steal are strengthened by precise definitions of the measured parameters and innovative applications of technology.