Scientists say a 43-year old psychiatrist in France spent an hour on the telephone talking to a patient, cradling the receiver between his left ear and shoulder so he could keep his hands free.
Shortly afterwards he experienced a temporary blindness in his left eye, together with a ringing in his left ear and a difficulty in speaking.
An angiogram of the patient's brain showed he had ruptured the carotid artery, a vital blood vessel supplying the brain, eyes and other parts of the head.
The psychiatrist had no predisposition to arterial disease, but a CT scan showed a bony structure was directly in contact with his internal carotid artery.
This was his styloid process, a slender, pointed bone which runs from both sides of the skull under the ears and behind the jaw.
Although everyone has two, the man's was unusually long, and was the cause of the rupture.
In this case, the psychiatrist's symptoms disappeared within a few hours.
Anti-coagulants
He was prescribed anti-coagulants for three months to prevent his blood from clotting.
Dr Mathieu Zuber, a neurologist at Sainte-Anne Hospital in Paris, who reported the case, said long styroid processes could be a more common cause of tears, or dissections, in the walls of the carotid artery than previously thought.
He said around 20% of strokes in young adults were caused by dissections.
Dr Zuber said: "Fortunately, this patient had only a transient ischaemic attack, or a brief interruption in blood flow to the brain that resolved in less than 24 hours.
"But this case shows us that everyday activities with a prolonged distortion of the neck, such as holding the phone between your ear and shoulder, can have unpredictable consequences for some people.
"Unfortunately, there is no simple procedure to identify people with long styroid processes. There haven't been any studies to determine how common these are, but they could be occurring more frequently than was generally thought."
The psychiatrist has had no more symptoms, but now avoids holding the telephone between his ear and shoulder for long periods at a time.
The study was reported in the November issue of Neurology, the journal of the American Academy of Neurology.
Background Briefings
Medical notes
Mobile phone 'brain risk'
(06 Nov 99 | Health)
Stroke care 'disorganised and haphazard'
(12 Oct 99 | Health)
Minor strokes: The health risks
(08 Oct 99 | Medical notes)
MPs study mobile phone health fears
(15 Jun 99 | Health)
Stroke Association
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American Academy of Neurology
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