There's a wonderful episode in Toby Young's How to Lose Friends and Alienate People - a record of his disastrous stint working as a journalist in New York - when the hapless hack wakes up one morning to discover that half his face is paralysed. Convinced he has suffered a "coke stroke" - brought on by excessive consumption of Class A narcotics - he rushes to his doctor who diagnoses a condition called Bell's Palsy before shamelessly inquiring if Young has any idea where he himself can get some.
It's one of the funniest anecdotes in the book. Or at least it was until I myself recently came down with Bell's Palsy, at which point the idea of wonky faces and dribbling mouths suddenly became a lot less amusing.
Named after Sir Charles Bell, the 19th-century surgeon who first described the condition, Bell's Palsy is an inflammation of the seventh cranial nerve, the matrix of 7,000 nerve fibres that control the muscles of the face (and hence all facial movement and expression). In 99 per cent of cases it affects only one side of the face, and although an estimated one in 70 of the UK population will suffer from it at some point in their lifetime, there is still no medical consensus as to what causes it. Latest research has suggested it probably has a viral trigger (my own symptoms arrived soon after an acute chest infection).
The paralysis comes on swiftly and with no obvious warning signs. I went to bed one evening looking normal, but when I woke the next morning the entire right side of my face seemed to have slipped an inch below the left, leaving me looking like a partially melted waxwork. I couldn't close my eye properly; my mouth had rearranged itself into a diagonal rather than horizontal line; and I had no right-side facial movement, as if I had undergone a particularly intense course of botox.
So dramatic was the transformation, and so sudden, that, like Toby Young, my immediate thought was that I'd suffered a stroke. Fortunately my wife's uncle had had the condition a couple of months previously and she provided a diagnosis.
Although visually alarming, Bell's Palsy is not in itself either dangerous or life threatening. It is certainly uncomfortable - imagine an invisible hand clamped to the side of your face constantly dragging your features downwards - and, if you are not careful, can lead to some unpleasant complications. The cornea, for instance, can dry out because you can't close your eye or blink properly (in the early stages sufferers are advised to use eye drops or wear a patch).
There is also a considerable amount of mess involved, especially when eating and drinking. The morning I discovered I had the condition I went downstairs and, as usual, glugged some orange juice out of a carton, only to discover that, because I had no muscle control over one side of my mouth, most of the juice ended up down my shirt. For the next two weeks I had to do most of my drinking through a straw and could only chew properly by holding my lips closed with my fingers.
While it is a physical nuisance, the palsy's real impact is psychological: the sense that, with your face all lopsided, you have somehow lost your identity.
Over the years I have done all sorts of weird and humiliating things, from working as a stand-up comedian to handing out leaflets on Oxford Street dressed as a giant tomato. Never, however, have I felt so acutely self-conscious as I did with my palsied countenance. You imagine that people are constantly looking at you; feel a need to justify your looks to everyone with whom you come into contact, to insist that this is just a temporary affliction and that you haven't always been like this.
A week after being struck down I had to deliver a lecture in Copenhagen. It was excruciating, not least because, unable to work my mouth properly, I kept slurring my words, leading many audience members to complain that I was drunk. It gives you a real insight into how alienating it must be for people with serious facial deformities; how dependent our sense of social inclusion is upon conformity of appearance.
To date there is no easy cure for Bell's Palsy. Like most sufferers I was prescribed a course of steroids and anti-viral drugs as soon as the condition came on, and given a set of facial exercises to perform to get the nerve signals moving again.
Whether any of this actually works, however, is unclear. The bottom line is that you just have to sit it out. Eighty per cent of sufferers recover completely within three months. The remaining 20 per cent can take anything up to two years to get better, with a minority never regaining full facial movement. I have now had the condition for 12 weeks, and still have a slightly droopy eye and slanted mouth.
My one consolation is that at least I am in good company. Past sufferers from Bell's include George Clooney, Pierce Brosnan, Ralph Nader and, a personal hero, Rick Savage of Def Leppard. And in a bizarre way, now that the worst is past, I have come to rather appreciate my asymmetrical appearance. "You used to look a bit plain," a friend told me the other day. "Now you've got this cool sneer."
Maybe not being the person I was before isn't such a bad thing after all.
Paul Sussman's new novel The Last Secret of the Temple is out in July, published by Bantam Press, £10.99