The etiology of RPON is still unknown and remains controversial - some scientists believe that RPON is a subtype of migraine, while others believe that it is a<unk> c disorder. As such, different potential etiologic mechanisms have been proposed based on case reports, including migrainous and<unk> c mechanisms. Yet, the renaming of RPON from OM indicates that the<unk> c cause may play a more important role than the migrainous cause in the pathophysiology of RPON. Migrainous mechanism RPON was previously thought to be having a migrainous origin since it shares some common characteristics with migraine, and their only differences are the intensity and duration of headaches. Therefore, it was postulated that migraine caused<unk>  in RPON. However, the major argument against a migrainous origin is the long latency period between the onset of headache and<unk>  (up to 14 days), which is not consistent with a typical migraine. Nevertheless, several migrainous mechanisms have been proposed. Nerve compression Compression mechanism is the first theory postulated regarding the pathophysiology of RPON. It is proposed that headache is caused by direct pressure on CNIII (compression<unk>  within the cavernous sinus due to edema of the walls of the internal carotid artery (ICA) or posterior cerebral artery (PCA) during migraine episodes. Ischemia Cavernous section of the ICA and a perforating vessel from the proximal PCA are responsible for supplying CNIII, CNIV, and CNVI. During migraine attacks, vasoconstriction of the ICA and PCA may lead to a reversible and ischemic breakdown of the blood-brain barrier. The blood-brain barrier breakdown results in vasogenic edema, which promotes the development of RPON. Neuropeptides-induced Alternatively, it is proposed that migraine-related release of neuropeptides from trigeminal nerve fibers terminating on the circle of Willis might be the cause. Some of the neuropeptides released are potentially toxic, and may induce blood-brain barrier breakdown that accounts for<unk> .<unk> c mechanism Additional models have been proposed to explain the cause of RPON. The thickened and enhanced symptomatic nerve, as shown in recent MRI findings, might be indicative of the existence of structural nerve damage in RPON. Therefore,<unk>  is suggested as the primary cause of RPON, either induced by<unk>  viral infections or immune-mediated inflammation. However, cerebrospinal fluid (CSF) analyses are normal in the vast majority of RPON cases, which is inconsistent with the findings of autoimmune or inflammatory-mediated pathomechanism. Nevertheless, several<unk> c mechanisms have been proposed. Benign viral infection The enhancement and thickening of the oculomotor nerve can occur in a variety of infectious inflammatory conditions. However, spontaneous resolution is unlikely to occur in viral infection, except for benign viral infection that usually causes mild or no symptoms in humans. Therefore, benign viral infection could be an explanation for the development of RPON. Immune-mediated inflammation Recent MRI findings have led to the current understanding of RPON as an inflammation-induced<unk> .<unk>  demyelinating<unk>  is proposed as a pathophysiological pathway because similar MRI findings have been observed in both RPON and chronic inflammatory demyelinating<unk> . Inflammatory demyelination of the ocular cranial nerves would likely lead to the release of neuropeptides, such as calcitonin gene-related peptide, to the trigeminovascular system. This would irritate the trigeminal sensory fibers, and consequently, a headache as manifested in RPON is triggered.
Recurrent painful ophthalmoplegic neuropathy
Acute visual loss
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Persistent edema of rosacea
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Diffuse unilateral subacute neuroretinitis
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Facial onset sensory and motor neuropathy