Large frontal osteoma

Mucosal thickening in both maxillary sinuses, mild on the right.
Sclerotic lesion on the left side of the frontal sinus, measuring 3.2 x 2.2 cm - osteoma, most probably.

NB: the last sequences are centered on the paranasal sinuses and are "blown up".

Osteoma measuring 3.1 x 2.5 x 2.8 cm with lobulated irregular border on the left side of the frontal sinus, expanding through the sinus's posterior border and indenting and compressing the adjacent brain.
Polypoid mucosal thickening in all paranasal sinuses and nasal cavity, excluding the sphenoid sinus which is occluded and full of fluid. The polypoid ethmoidal mucosa invades the nasal cavity on both sides. No evidence of bone destruction.
Bilateral orbital contents are normal.

Diffuse periventricular and discrete white matter microangiopathy, the latter scattered in all cerebral lobes with peripheral predominance. Small right frontal non-acute infarct.
No abnormal focal finding in the posterior fossa.
No intracranial blood products and no acute ischemia causing restricted diffusion.
No pathological intracranial enhancement after gadolinium injection. Normal signals from the intracranial arteries and veins. Prominent atheromatous plaques in the right vertebral artery and cavernous-supraclinoid internal carotid arteries, more so on the right with wall thickening.

Free craniocervical junction.

In summary;
Large left frontal sinus osteoma and sinonasal polyposis.
Supratentorial microangiopathy.

CT head, done due to head trauma, 4 months after the MRI:

No evidence of intracranial bleed or skull or any fracture.

Status post bifrontal craniotomy, excision of frontal osteoma, and frontal sinus fat obliteration. Status post bilateral middle turbinectomy, ethmoidectomy, and maxillary antrostomy. Persistent mucosal thickening in remaining ethmoidal air cells and maxillary sinuses and bilateral opacification of the sphenoid sinus.

Coarsely ossified posterior longitudinal ligament at the level of C3-C5; status post posterior laminectomy in C3-C5 (seen on the MRI study in retrospect).