Nonarteritic Anterior Ischemic Optic Neuropathy and Stroke in Young.

Sir,

We read with interest the article titled “A hospital-based study of stroke in young from North East India” by Hussain et al.[1] Authors have mentioned that neurosyphilis (NS) is an important risk factor for stroke in young. Even though not mentioned in recent studies, NS still remains relevant. We appreciate the author's effort and research. We would like to highlight few points regarding (i) syphilis-induced nonarteritic anterior ischemic optic neuropathy (NAION) which might coexist in stroke in young; (ii) importance of periodical ocular examination in young hypertensive stroke patients; (iii) and importance of identifying crowded disc in young diabetic stroke patients.

NAION is an acute ischemic disorder of the optic nerve head which might be associated with various systemic disease (syphilis, hypertension, and diabetes) at its onset.[2] Syphilis is an imitator of disease. Visual loss from optic nerve involvement may be the first manifestation of syphilis and HIV coinfection.[3] Patients usually have disc edema and mild visual dysfunction. Syphilitic optic neuropathy (SON) has an excellent prognosis if the disease is diagnosed promptly and treated properly. In SON, disc edema is diffuse, elevated and not associated with hemorrhage or exudate. These findings are nonspecific; hence, the diagnosis could not be based solely on the optic disc appearance. Anemia and arterial hypotension may be associated with NAION.[2] Tabes dorsalis is a neurogenic cause for orthostatic hypotension.[4] Anemia is a common problem in India. If NS is suspected, blood transfusion-induced infection should be considered, which might occur without a history of primary lesion.

Nocturnal arterial hypotension may be an important risk factor in the development of anterior ischemic optic neuropathy.[2] NAION patients on oral hypotensive medication showed a significant correlation between progressive visual deterioration and nocturnal arterial hypotension. The most common cause for this correlation is aggressive hypotensive therapy at bedtime. Such a therapeutic regime should be investigated and if possible, corrected in consultation with physician.

Acute elevation in intraocular pressure (IOP) and small optic disc with cup-disc ratio of <30%[5] are ocular risk factors for NAION. Elevated IOP impairs ocular perfusion pressure. Subclinical low-grade optic nerve ischemia due to elevated IOP may present as asymptomatic optic disc swelling initially. Subsequent progressive ischemia results in frank bouts of symptomatic NAION. The treatment of hyperglycemia may cause crystalline lens swelling and raised IOP.

To conclude, IOP should be periodically evaluated in stroke (young diabetic) patients who develop asymptomatic disc edema in crowded disc.

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