EMM_385.fm Page 447 Friday, November 8, 2002 11:16 AM Emergency Medicine (2002) 14, 447– 449 Blackwell Science, Ltd Case Report ICH and olfactory hallucinations Intracerebral haemorrhage presenting as olfactory hallucinations Elizabeth Nye and Glenn Arendts Department of Emergency Medicine, St George Hospital, Sydney, New South Wales, Australia Abstract Isolated olfactory hallucinations are a rare event and have been associated with a number of aetiologies including seizures, migraines and psychiatric illnesses. This case report describes a 58-year-old woman with an unusual haemorrhagic lesion as the cause of her olfactory symptoms. A review of the literature concerning the causes and management recommendations for olfactory hallucinations is presented. Key words: haemorrhage, hallucinations, olfactory, stroke. Case report A 58-year-old woman self-presented to the emergency department with an increasing frequency of experiencing abnormal olfactory sensations that had started 4 days earlier. She complained of episodically smelling a very unpleasant odour that was like ‘burning paint mixed with rotting flesh’. The odour would increase in intensity before subsiding and the duration of each episode was 2–3 min. The episodes were similar in nature with no identifiable precipitating factors. On the first day she had three episodes, but by the time of presentation she was symptomatic every 45 min. The only symptoms reported between episodes were of food tasting different, as if it had lost some taste, and a mild diffuse headache for which she did not take analgesia. She had not noticed any loss of smell and there were no other neurological symptoms on detailed inquiry. She had no previous history of neurological or psychiatric disorders, significant head injury or hypertension. There was no family history of seizure disorders. Her Correspondence: only medication was hormone replacement therapy with oestrone sulfate and norethisterone. On presentation she was afebrile, her heart rate was 68/min and blood pressure 130/85 mmHg. No abnormalities were detected on neurological examination. In particular there was no limb weakness, parasthesia, quadrantanopia or other cranial nerve deficits, although smell and taste were not formally assessed. Higher neurological functions including orientation, speech, and frontal and parietal lobe tasks were normal, as was an ear, nose and throat examination. There were no features of psychiatric illness present. The patient suffered further episodes whilst in the ED, which were witnessed by staff and during which the patient described her symptoms. Throughout these periods she remained alert and orientated, ECG monitoring and vital signs were normal, and no abnormal movements were observed. Initial investigation results, comprising a full blood count, coagulation profile, electrolytes, and renal and hepatic function, were all within normal limits. Dr Glenn Arendts, Department of Emergency Medicine, St George Hospital, Gray St, Kogarah, NSW, Australia. Email: arendtsg@sesahs.nsw.gov.au Elizabeth Nye, MBBS, Resident Medical Officer; Glenn Arendts, MBBS, FACEM, Staff Specialist. EMM_385.fm Page 448 Friday, November 8, 2002 11:16 AM E Nye and G Arendts admission she was discharged with neurology review scheduled for 3 months later. At this appointment the patient remained well with a repeat EEG again showing changes of a left-sided temporal lesion but no seizure activity. Discussion Figure 1. Cranial computerized tomography scan demonstrates a solitary 3 × 2 × 2 cm haemorrhagic lesion in the left uncinate lobe. The provisional diagnosis was of a cerebral tumour causing isolated olfactory hallucinations. A cranial CT scan with and without intravenous contrast was performed (Fig. 1). This demonstrated a solitary 3 × 2 × 2 cm haemorrhagic lesion in the left uncinate lobe, without evidence of midline shift or cerebral oedema. There was no radiological evidence of primary or secondary neoplasia. The consultant radiologist who interpreted the CT scan reported the haemorrhage was most likely due to small vessel disease, and further imaging by cerebral angiography was not performed. The patient was admitted under the care of a neurologist and anticonvulsant therapy was commenced in the form of clonazepam 0.25 mg twice daily and phenytoin 300 mg daily (following an oral loading dose of 1000 mg over 24 h). An EEG performed on the fourth day of admission when the patient was asymptomatic showed no seizure activity but demonstrated sharp transient waves in the left temporal lobe consistent with a left sided structural lesion. The patient remained stable on anticonvulsant therapy with diminution and eventual elimination of her symptoms 6 days after admission. Ten days after 448 The subject in this report presented with a primary intracerebral haemorrhage that manifested itself as isolated olfactory hallucinations. We found no reported similar cases in a search of the Medline-listed literature using the keywords ‘olfactory’, ‘hallucinations’ and ‘seizures’. Several authors have identified temporal lobe tumours and hippocampal sclerosis as the most common neuropathologies associated with olfactory hallucinations.1,2 These authors described patients who had olfactory auras as isolated phenomena, however, the olfactory symptoms were more commonly associated with other features of complex partial or generalized seizures. Primary intracerebral haemorrhage is usually associated with hypertension 3 but the subject of this report had no history of hypertension and had daily systolic blood pressure measurements below 140 mmHg throughout her admission. Initial CT scans with and without contrast did not suggest an underlying tumour or vascular malformation. Although hormone replacement therapy may predispose to cerebral haemorrhage in the context of cerebral venous thrombus3 there were no other clinical or radiological findings to support such a diagnosis in this case. Amyloid angiopathy is increasingly thought to be a cause of non-traumatic intraparenchymal haemorrhage, but is difficult to diagnose in the absence of specimen histology obtained through a postmortem examination.4 The functional anatomy of the sense of smell is complex and poorly understood, involving diverse areas of the brain including the uncinate lobe, amygdala, orbitofrontal cortex and limbic system.5,6 The initial connection of the olfactory tract is to the primary olfactory cortex and the amygdala. The primary olfactory cortex, called the piriform cortex, is located in the uncus and anterior parahippocampal gyrus, and is thought to be associated with the perception of smell. Olfactory hallucinations have most often been associated with lesions of the mesial temporal lobe; however, they have also been reported in association with lesions of the orbitofrontal region.7 EMM_385.fm Page 449 Friday, November 8, 2002 11:16 AM ICH and olfactory hallucinations Olfactory and other temporal lobe symptoms can be reproduced by electrical stimulation of these regions.8 In the case we have described the symptoms correlate with an anatomical lesion of the uncinate gyrus. The true prevalence of olfactory hallucinations is difficult to determine due to variations in the classification of olfactory phenomena as seizures, auras, illusions or hallucinations.9 In a retrospective review of 1423 patients with intractable partial seizures, Acharya et al. found that the prevalence of olfactory aura was only 0.9%;2 however, the prevalence has been reported to be as high as 16% in other smaller series.10 Fried et al. reported that seven out of 37 patients (18.9%) who remained seizure free after surgery for hippocampal sclerosis continued to have auras, including olfactory auras, without seizures.1 This suggests some anatomical separation of the sites responsible for the aura and other temporal lobe seizure activity. Olfactory hallucinations have been reported in association with migraine, but in these cases the aura always lasts longer than 5 min and is associated with a headache that fulfils the diagnostic criteria for migraine.11 Despite the lack of precise data, it is clear olfactory hallucinations with or without other neurological symptoms are rare. It is therefore not surprising that there is a paucity of evidence-based literature to guide investigation and management of such cases. Non-auditory hallucinations are highly suggestive of organic disease12 and such patients should have a thorough assessment including mandatory neuroradiological investigation for a temporal or extratemporal tumour. In this case the patient was commenced on phenytoin and clonazepam, and there was a reduction in the frequency of her symptoms from every 45 min at presentation to being asymptomatic within 6 days of commencing this treatment. Three months later she remained well, but longer-term follow-up of the patient will be required to further assess the efficacy of this drug regime. It is worth noting that there was no evidence of seizure activity on either the initial EEG or the subsequent EEG performed 3 months later. It is therefore impossible to know whether the rapid resolution of this patient’s symptoms is a true response to anticonvulsant therapy or simply represents the natural history of this uncommon condition. We could find no literature in refereed journals concerning conventional anticonvulsant therapy for isolated olfactory symptoms. Neurosurgery, particularly amygdalectomy, has been successful in some patients with intractable olfactory seizures.1,13 Conclusion Isolated olfactory hallucinations are rare. Although most cases are associated with mesial temporal sclerosis or tumours, other temporal lesions, such as primary intracerebral haemorrhage as occurred in this case, should be considered as possible aetiologies. Treatment with anticonvulsants may control symptoms. Accepted 20 May 2002 References 1. Freid I, Spencer DD, Spencer SS. The anatomy of epileptic auras: Focal pathology and surgical outcome. J. Neurosurg. 1995; 83: 60 – 6. 2. Acharya V, Acharya J, Luders H. Olfactory epileptic auras. Neurology 1998; 51: 56 – 61. 3. Radberg JA, Olsson JE, Radberg CT. Prognostic parameters in spontaneous intracerebral haemorrhage with special reference to anticoagulant treatment. Stroke 1991; 22: 571– 6. 4. Vinters HV. Cerebral amyloid angiopathy. A critical review. Stroke 1987; 18: 311–24. 5. Quereshy A, Kawashima R, Imran MB et al. Functional mapping of the human brain in olfactory processing: A PET study. J. Neurophysiol. 2000; 84: 1656 – 66. 6. 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