[To the differential diagnosis of cranial nerve lesions: the progressive necrotising external otitis (author's transl)].

A review of necrotising external otitis, a relatively unknown and dangerous disease, brings out that, initially, it has three characteristics: a granulating necrotising ostitis of the external meatus, extreme pain and a yellowish green secretion. It is always caused by a pseudomonas infection and in almost all cases the patients suffer from diabetes mellitus. If the condition is not recognized in good time and an extensive debridement of the bone involved not performed promptly, ostomyelitis of the base of the skull may follow with involvement of cranial nerves. Severe chronic osteomyelitis of cervical vertebrae occurred in one of our cases. The neurologist must bear this disease in mind in the differential diagnosis when cranial nerves are affected because the nerve disturbances may become evident only after the local condition has subsided or the nerve deficits may be more prominent than and obscure the local ear condition. The most commonly involved nerve is the facial although there may be multiple cranial nerves involved including the third through the twelfth. If the cervical vertebrae become affected there may be nerve root lesions. A torpid meningoencephalitis may also occur. Close cooperation between otologists and neurologists is necessary to recognize and treat these conditions properly.