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. Diagnosis
Diagnostic criteria
To be diagnosed with RPON, a person must have a minimum of 2 unilateral headache attacks with ipsilateral ocular cranial nerve paralysis that cannot be explained by other causes of headache in ICHD-3 after investigation. Diagnostic tests
RPON is a diagnosis of exclusion, meaning that other conditions with similar clinical presentation, such as vascular, inflammatory, neoplastic, and infectious causes, must be ruled out before the confirmation of RPON diagnosis. Physical examination, neuroimaging, and laboratory tests are routinely conducted in clinical practice to evaluate this disease. Physical examination
After obtaining the medical history of people with suspected RPON, thorough eye examination and neurological examination are usually performed to assess the extent of neurological impairment, localize the brain regions being affected, and rule out other possible causes for the symptoms. These involve the assessments of visual acuity, eye movements and alignment, pupillary responses, and mental status. Neuroimaging
Contrast-enhanced magnetic resonance imaging (MRI) is a diagnostic tool that can facilitate the differentiation of RPON from other diseases. The transient, reversible enhancement or thickening of the ocular motor nerve(s), which can be observed in the MRI scans of a small proportion of affected individuals during acute attacks, is a distinguishing feature of RPON.
Trimethobenzamide (trade names Tebamide, Tigan) is an antiemetic used to prevent nausea and vomiting. Mechanism of action
Trimethobenzamide is an antagonist of the D2 receptor. It is believed to affect the chemoreceptor trigger zone (CTZ) of the medulla oblongata to suppress nausea and vomiting. Side effects
Possible side effects include drowsiness, dizziness, headache, muscle cramps, and blurred vision. More serious adverse effects include skin rash, tremors, parkinsonism, and jaundice. Formulations
Trimethobenzamide is marketed under the brand names Tebamide and Tigan, manufactured by GlaxoSmithKline and King Pharmaceuticals, respectively. It is available as oral capsules and injectable formulations. Trimethobenzamide was also available as a rectal suppository, but such formulations were banned by the U.S. Food and Drug Administration on April 6, 2007, due to unproven efficacy. Synthesis
Alkylation of the sodium salt of p-hydroxybenzaldehyde (1) with 2-dimethylaminoethyl chloride affords the ether (2). Reductive amination of the aldehyde in the presence of ammonia gives diamine (3). Acylation of that product with 3,4,5-trimethoxybenzoyl chloride affords trimethobenzamide (4). See also
Domperidone
Metoclopramide

References
External links
Tebamide
Tigan (manufacturers website)