Well I do have a diagnosis although, as with many rare and odd medical cases, it is not a 100% nailed-down with certainty. I have (and appear to still have) neurosarcoidosis.
Neurosarcoidosis (sometimes shortened to neurosarcoid) refers to sarcoidosis, a condition of unknown cause featuring granulomas in various tissues, involving the central nervous system (brain and spinal cord). It can have many manifestations, but abnormalities of the cranial nerves (a group of twelve nerves supplying the head and neck area) are the most common. It may develop acutely, subacutely, and chronically. Approximately 5-10% of people with sarcoidosis of other organs (e.g. lung) develop central nervous system involvement. Only 1% of people with sarcoidosis will have neurosarcoidosis alone without involvement of any other organs. Diagnosis can be difficult, with no test apart from biopsy being completely reliable. Treatment is with immunosuppression. The first case of sarcoidosis involving the nervous system was reported in 1948. – Wikipedia, All text is available under the terms of the GNU Free Documentation License.
It seems that reducing the steroid dose to 10mg a day has allowed various symptoms to return, my eyes, or more accurately the muscle around my eyes, don’t work properly and ache all day. On the higher dose they worked fine until 4-5pm. My face has also started to ‘freeze’ or ‘spasm’ intermittently.
So, we are increasing the dose back to 20mg a day for 2 weeks, 15mg for 2 weeks, 10mg a day for 2 weeks and some more MRI scans of my brain and spine in the meantime.