this is unfortunate to hear. things that come to mind might be a metabolic cause or hormonal issue. beyond this I'm guessing they have obtained a CT and MRI of your head to look for any abnormalities. Have you seen a neurologist? This appears neurogenic. I am an orthopedic surgeon so my insight is limited.
2011.75 Jet Black e92 ///
M3: ZCP|6MT|BB interior|Turner Motorsport black pedals|IND
Edition Cosmetic Package |LUX 5K|35% tint|clear-bra|Vorsteiner GTS-V diffuser