True middle meningeal artery aneurysms (MMAAs) are an exceedingly rare entity, with less than 20 cases reported in the literature and only one of them being a giant aneurysm reported in a patient with fibrous dysplasia according to Ramirez et al. These aneurysms don’t usually grow beyond 10 mm in diameter, so misdiagnosing such lesions usually involves other vascular diagnostic possibilities such as brain aneurysms in a different anatomic location, brain arteriovenous malformations (AVMs) or dural arteriovenous fistulae (DAVFs) [1].

As reported by Salazar et al. giant thrombosed aneurysms suppose a difficult diagnosis and can be misdiagnosed as meningiomas on initial images in up to 54% of cases, this misdiagnosis can lead to high mortality when the diagnosis is confirmed during surgery rather than before the surgical intervention [2]. Furthermore these lesions can manifest in three different ways, such as pseudotumoral syndromes and slow progression of symptoms (as was in our case), with sub-arachnoid bleeding or brain ischemia (which represent more typical behavior of vascular lesions) [2].

This case presents an unprecedented type of vascular lesion, adding to the neurosurgeon armamentarium a new possible differential diagnosis in difficult cases.

This lesion entails a quadruple rarity combination of characteristics: (1) True middle meningeal artery aneurysm, (2) Giant aneurysm, (3) Totally thrombosed and (4) Pseudotumoral behavior, these characteristics make this case the first of its kind in English Neurosurgical literature to the best of the authors knowledge.