gms | German Medical Science

Inflammations of the external ear canal are a very common diagnosis in the ENT surgeon’s daily practice. Pseudomonas aeruginosa infection bears the risk of malignant external otitis, which can lead to an affection of the lateral skull base in the region of the apex of the petrous bone [Ref. 1]. Inflammation of the petrous bone and the infratemporal fossa, however, may as well occur without the typical signs of malignant external otitis [Ref. 2]. Furthermore, it is known that even patients without the typical risk factors such as diabetes mellitus or HIV can be affected by pseudomonas-induced skull base complications [Ref. 3], which prove true in our patient collective.

Between January 2004 and June 2004 we diagnosed osteomyelitis of the lateral and central skull base in four cases. Three of the patients had been treated for pseudomonas infection of the outer ear canal, one first presented with signs of a residual middle ear infection. Very severe headache and ear pain and cranial nerve palsies resulted in further investigation and diagnosis. We present the four cases and their 5 to 15 months follow-up results. Diagnostic steps and different therapeutic options are discussed.

Patient 1 presented with permanent right sided ear pain after ear canal abscess drainage. Because local treatment had failed to help, we performed curettage of the outer ear canal. The microbiological smear showed the growth of pseudomonas aeruginosa. In the CT scan there was no bony destruction at this point, nor was there any radiological sign of mastoiditis. The patients’ symptoms declined under systemic ciprofloxacin medication. 4 ½ months later the patient developed a paralysis of the cranial nerves Nn. IX, X, XI, and XII. When performing actual CT and MRI scans we detected an inflammatory or tumorous pathologic structure involving the right lateral skull base, clivus and condylus, and an occlusion of right jugular vein bulb as well as a 50% stenosis of right internal carotid artery (Figure 1 [Fig. 1]). In order to differentiate an inflammatory process from malignancy the patient underwent navigation-assisted, transcervical-transmastoidal biopsy and paracentesis. Histologically, no signs of malignancy were found, but inflammatory T-lymphocytic infiltration. Under intravenous (i.v.) application of high dose piperacillin/tazobactam and ciprofloxacin, which had been started in agreement with the department of infectiology, clinical state of the patient stabilized but did not improve. Therefore we performed a second biopsy via transnasal approach (navigation-assisted) and – in order to prevent further aspiration – decided for tracheostomy as well as percutaneus endoscopic gastrostomy (PEG). Former histology was confirmed, and treatment was continued with antibiotics and symptomatic treatment. One month after first i.v. antibiotic dose, a slow restitution of cranial nerve functions began, and indicators of inflammation normalized quickly. The patient was referred to a rehabilitation clinic for four weeks. During the following 5 months of oral ciprofloxacin treatment, function of cranial nerves IX and XII recovered completely, and the patient appeared to compensate well vocal cord paralysis and lesion of N. XI. We monitored a continuous decline of contrast medium (cm) enhancement in the MRI scans over the following months – with complete resolution 13 months after first i.v. antibiotics.

Patient 2 initially presented with right-sided ear pain and signs of a down going middle ear infection. Three months later he developed paralysis of ipsilateral cranial nerves VI, IX, and X as well as dysphagia and massive temporal headache and neck pain. The MRI scan detected an inflammatory or tumorous pathology of the petrous bone, affecting the infratemporal and pterygopalatine fossae, jugular foramen, cavernous sinus, and retroclival, epi- and hypopharyngeal regions. Again, we discussed the case interdiciplinarily (neurology, infectiology, neuroradiology) and decided for a combined strategy including limited surgery (mastoidectomy), high dose i.v. piperacillin/tazobactam and ciprofloxacin, hyperbaric oxygen therapy and PEG/symptomatic treatment. 3 weeks after the operation, a slow restitution of cranial nerve function occurred. 7 weeks after surgery the patient was referred to the rehabilitation clinic, treatment was continued in the same way as in the first patient. During 4 months of follow-up we monitored an improvement of results (clinically and radiologically). Now we are planning to remove the PEG. However, there is residual functio laesa of cranial nerves IX and X.

Patient 3 (aged 89 years) had a local resection of pseudomonas-infected tissue in the left outer ear canal after which initial symptoms declined under systemic application of ciprofloxacin. He had revision surgery two months later for recurrent pain and bony destruction of the mastoid cavity in the CT scan (suspected osteomyelitis), and again he initially recovered well. Nevertheless he developed paralysis of cranial nerves VI, VIII, X, and XII four months after the first operation. The MRI scan showed an inflammation of the petrous bone apex spreading to the region of large cervical vessels. Because in his case, a loss of function of the eighth nerve already existed, we decided for subtotal petrosectomy and high dose i.v. piperacillin/tazobactam and ciprofloxacin. This patient recovered relatively quickly, compensated well his loss of left sided peripheral vestibular function and hearing, and after normalisation of inflammation parameters he was referred to a rehabilitation clinic 4 weeks after surgery. Ciprofloxacin medication was kept up over 4 months. 13 months after the radical operation there is only a residual minimal cm-enhancement, the patient is well, cranial nerve function is fully restored.

Patient 4 was the only one with diabetes as a predisposing factor to malignant otitis. For left-sided outer ear canal pseudomonas inflammation which had been resistant to local treatment and showed mastoid involvement, he underwent mastoidectomy. Despite the operation he developed cranial nerve paralysis of VII, IX, X, and XII, as well as Horner’s syndrome. The MRI showed a widespread pathology of the mediobasal temporal bone, clivus, condylus, and parapharyngeal soft tissue. Occlusion of the internal carotid artery/medial meningeal artery caused cerebral ischaemia. Under i.v. high dose ciprofloxacin the cranial nerve function began to recover, and under oral ciprofloxacin over 3 more months he was referred to a neurological rehabilitation clinic without nasogastric feeding tube 4 weeks after i.v. therapy had been started. In the MRI scans cm-enhancement resolved completely within the following 3 months, only minimal residual functional lesions of facial and hypoglossal nerves are still detectable, the patient is well.

If external otitis with evidence of Pseudomonas aeruginosa proves to be resistant to therapy and is exceptionally painful, we strongly recommend CT and MRI scans of the lateral skull base and detailed analysis of cranial nerve function. In these patients, especially in the case of concomitant diabetes or other immunocompromising disease, it is essential to think of temporal bone osteomyelitis as a possible complication. The patient's clinical history and symptoms, physical examination findings, evidence of pseudomonas presence, CT and MRI scans and possibly scintigraphy of the skull base, are important to find the correct diagnosis. In some cases histology is helpful to exclude malignancy which is often difficult to distinguish from osteomyelitis [Ref. 4]. Once the diagnosis of osteomyelitis of petrosal apex is confirmed, one must thoroughly evaluate a radical-surgical against a conservative therapeutic approach. Depending on the severity of symptoms, and with respect to the patient’s general health condition, age, and previous illnesses, the risk of the operation has to be weighed against the risk of leaving the infected tissue in situ [Ref. 5], [Ref. 6].

However, according to our experience and the literature, a long-term antibiotic treatment with quinolones is to be preferred in most cases [Ref. 7], [Ref. 8] In severe cases an additional hyperbaric oxygen therapy should be considered and performed, if there is no contraindication. Normalization of inflammation parameters, decline of cm-enhancement in the MRI, and clinical improvement of the patient’s state are the factors that indicate when to go off the antibiotic treatment [Ref. 5].