THE TRAGIC early death of Mo Mowlam has drawn attention to the 16,000 diagnoses of brain tumours in the UK each year. Forty per cent of these are tumours that have started in the brain; the other 60 per cent have spread to the brain from cancers elsewhere in the body. Unfortunately, the primary tumours are no respecter of youth and, because younger people are often sufferers from primary brain tumours, these rank fourth among cancers in terms of years of life lost.

One of the early features of cerebral tumours is change in personality. If the frontal lobe is directly involved by the malignancy, or is affected by the increase in pressure within the skull, a patient’s character changes as the tumour grows. Many patients with a cerebral tumour become depressed, as did the late Sir Alan Clark, whose character apparently remained otherwise unscathed.

Classically, patients with a brain tumour affecting the frontal lobe become uninhibited, a pleasing earth- iness becomes coarseness, and flirtatiousness degenerates into crude sexual advances. The subtleties governing social or business behaviour are forgotten and as the tumour grows so niceties slide, so that the patient is guilty of errors of judgment. The sense of danger and propriety disappear. Attention and concentration are in short supply and sagacity is often replaced by an inappropriate euphoria. There are other physical signs that usually betray the telltale presence of the tumour. The MRI and CT scans have revolutionised the diagnosis of cerebral tumours.

About 20 years ago, the life of my social circle was enlivened by the wife of a well-known surgeon. Her case history is typical and illustrates the difficulty in appreciating changes in temperament when someone already has an unusual personality. Our friend had the reputation for holding views that were erudite but outrageous. She was thought of as the life and soul of the party, kindly but unpredictable, but even so her intellect determined that she was always treated with a certain amount of circumspection. There were times when she was abnormally depressed and anxious, but she hid her feelings successfully and continued her helter-skelter life.

Those who knew the surgeon’s wife well were aware that her family carried the genes for bipolar disorder (manic depression). Although showing no signs of psychosis, some of the characteristics of her personality were so well defined that it was possible to see that, should they ever become more pronounced, a diagnosis of bipolar disorder would be inevit-able. In late middle age, her behaviour began to deteriorate. What had once been a sharp, but jocular, put-down had become a savage riposte. What would have once been an amusing joke was so badly timed and inappropriate that it became cruel and tasteless. No longer was it a question of her opinions leading a conversation; she dominated it.

All those who knew the secret of the family history hoped that her husband was seeking the best psychiatric opinion. So he was. However, the psychiatrist and surgeon fell into one of the elephant traps of medicine, the dual pathology. The surgeon’s wife had indeed had her familial type of personality all her life but, although her recent symptoms were subtly different from her earlier ones, the differences had not been noticed. She had in fact developed a huge brain tumour. After most of it was removed, her cheerful, if unusual, personality was restored until, several years later, the remnants of the benign tumour regrew.

A quicker diagnosis was made by one of my senior colleagues when I was a junior hospital doctor. He had attended a fête that was being opened by the local landowner’s wife. The landowner was still in the Army and commanded a famous regiment. At the opening, the colonel’s wife’s behaviour was both aggressive and eccentric. My boss, who had been in the services, came back and asked me to make arrangements to admit her to hospital. He had seen the colonel after the f ête and, in a kindly but frank way, had said that, if this was his wife’s usual behaviour, he would never have been given the command. The doctor suggested that she should be investigated.

She too had a benign meningioma, the size of a large orange. It was removed in its entirety. She made a complete recovery and, once without her tumour, it was obvious that she was a charismatic woman with a charming and delightful personality. Forty years later, she died at a very ripe old age.

Mo Mowlam had mostly wonderful obituaries, most of which focused on her early life in politics, her youthful victories and her meteoric rise before she joined the Cabinet. I met her twice just before her condition was diagnosed. Once the diagnosis had been made public, her behaviour on these occasions immediately became understandable, and the need to understand that there is often a physical basis to personality became apparent.

Whereas I had been advised to expect a kindly, good-hearted, cheerful, hail-fellow-well-met personality, she was irritable, astoundingly aggressive and bigoted. We didn’t agree on much (if anything) but, although I hope that I remained firm but detached, she didn’t. Next time I met her, she was talking to a kindly Labour peer. I tried to scurry past, but he beckoned me over and said to Mo: “Do you know Tom Stuttaford?” The tumour, as yet undiagnosed, obviously hadn ’t affected her memory. “Yes,” she replied. “He is just a f***ing Tory and I don’t want to meet him.”

A very typical personality change, and very different from that seen when a now senior Times journalist, who at the time was a young reporter, had interviewed her. She was then helpful, affable, forthcoming and totally lacking in condescension and sectarianism.