Benign intracranial hypertension: correlation of cerebral blood flow with disease severity

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Abstract

Benign intracranial hypertension (BIH) is characterized by symptoms and signs of raised intracranial pressure in the absence of an intracranial mass lesion, infection or hydrocephalus. The purpose of this study was to evaluate the effect of disease severity on cerebral blood flow in patients with BIH on acetazolamide therapy. Methods: 11 patients (nine females, two males; mean age 30.5 years; range 22–29 years) with BIH were studied. All patients underwent CT and MRI scanning which were normal. The CSF pressure of all patients was above 200 mm H2O. All patients were under treatment with acetazolamide (1 g/day). Disease severity was determined by visual field examination and by clinical symptoms. Five patients were categorized into mild to moderate BIH (group I) and six patients had severe BIH (group II). All patients underwent perfusion brain SPECT with 740 MBq of Tc-99m-HMPAO. Results: brain perfusion abnormalities were observed in six of the 11 patients. One out of five patients in group I (20%) and five out of six patients (83%) in group II, had abnormal SPECT findings (P<0.04). In four patients of group II the left parietal lobe was involved and another patient had a right occipital abnormality. The single patient from group I with SPECT abnormalities demonstrated focal decreased perfusion in the left temporal area and decreased perfusion in the left caudate nucleus. Conclusion: patients with severe degree of BIH have a higher incidence of cerebral perfusion abnormalities. This group may have an increased risk of cerebrovascular complications. The continuous administration of acetazolamide which affects the vascular autoreactivity may contribute to the regional hypoperfusion. Further studies are recommended to evaluate the natural course of disease versus iatrogenic treatment effects.

Introduction

Benign intracranial hypertension (BIH) was defined for the first time by Dandy as a syndrome characterized by symptoms and signs of raised intracranial pressure in the absence of an intracranial mass lesion, infection or hydrocephalus in an otherwise healthy and alert patient [1].

The mechanism of increased CSF pressure in this disorder is still unclear. Involvement of the venous flow was presumed to be one of the causative mechanisms. Karahalios et al. [2] demonstrated that the cerebral venous pressure is elevated consistently in this patient group. Other conditions with increased venous pressure and cerebral blood volume are additional ambient factors which can initiate the BIH symptomatology. Only a few studies have been performed in order to study the cerebral blood flow (CBF) in these patients. In 1955, Foley et al. [3] found an increase of CBF in three patients with increased intracranial pressure, without discovering any other pathology. Raichle et al. [4] and Mathew et al. [5] demonstrated an increase of cerebral blood volume in two different studies. Raichle also found a decrease of the CBF in his 14 patient group. Baker et al. [6] reported similar results using Tc-99m-HMPAO brain SPECT.

Contrary to those findings, Brooks et al. [7] used a PET technique to analyze the oxygen utilization, blood flow and blood volume in five BIH patients and found no significant difference between this group and healthy controls.

In order to clarify the issue of abnormal CBF in BIH patients, we performed a perfusion brain SPECT study to a well-controlled patient group treated with acetazolamide.

Section snippets

Patient selection

Eleven patients (nine female, two male; mean age 30.5; range 22–39) were studied. All patients were diagnosed with BIH. The diagnosis was confirmed by neurological and neuro-ophthalmological examination and by lumbar CSF puncture. The CSF pressure of all patients was above the upper level limit of 200 mm H2O. All patients had normal CT and MRI scans. Disease severity was determined by the severity of papilledema and by visual field examination. Papilledema was graded: absent (grade 0), mild

Results

Brain perfusion abnormalities were observed in six of the 11 patients studied (54.5%). In group I, one of five patients (20%) had an abnormal SPECT finding, while in group II, five of six patients (83%) had abnormal SPECT findings. In four patients of group II the left parietal lobe was involved and another patient had a right occipital abnormality (Fig. 1). The difference in the number of abnormal SPECT findings between the two groups was statistically significant (P=0.04). The correlation

Discussion

Our data revealed a regional reduction of the cerebral blood flow in the cortex of patients with severe chronic benign intracranial hypertension under continuous treatment with acetazolamide. Previous studies which examined the cerebral blood flow in untreated patients demonstrated controversial results. Baker et al. [6] found hypoperfusion in 53% of the patients using SPECT technique. Gross et al. [8] who examined nine BIH patients, using Xe-133 inhalation technique, found elevated blood flow

Conclusion

Our findings support the assumption that there is a higher incidence of abnormal SPECT findings in patients with severe degree of BIH. Further studies are recommended to evaluate the natural course of disease versus iatrogenic treatment effects, as this may be of clinical and therapeutic significance.

Acknowledgements

We wish to extend our appreciation to Ms Shula Calman for her expert technical support in performing the SPECT studies. We would also like to thank Ms Mona Boaz (PhD candidate) for her skilful statistical analysis.

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