J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.38.1.52 on 1 January 1975. Downloaded from

Journal of Neurology, Neurosurgery, and Psychiatry, 1975, 38, 52-56

Non-invasive screening for surgical intracranial lesions

P. DANIEL SUBERVIOLA' AND N. DAVID GREYSON

From the Departments of Medicine (Neurology) and Radiological Sciences, The Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada

S YN OP SIS The value and reliability of the combined results of skull radiographs, electroencephalo- graphy, echoencephalography, isotope angiography, and brain scanning in 147 patients suspected of having an intracranial space occupying lesion are analysed. The overall accuracy of the technique was 7900. No false negatives were found. The advantages of adopting the system proposed by the authors in everyday clinical work is discussed.

The value of skull radiographs (Taveras and skull radiographs, electroencephalography, echo- Wood, 1964; Zimmer and Caplan, 1966; Pawl encephalography, isotope angiography, and brain 1969), electroencephalography scan in addition to at least one neuroradiological and Walter, 147 cases (EEG) (Daly and Thomas, 1958; Bagchi et al., contrast study were selected. There were available for final analysis; 75 females and 72 males. Protected by copyright. 1961; Magnus et al., 1961; Sidell and Daly, The youngest patient was 13 and the oldest 78 years, 1961; Small et al., 1961; Silverman, 1964; with an average age of 46-8 years. Murphy et al., 1967), echoencephalography The skull radiograph series-consisted of five films (Leksell, 1955, 1958; Lithander, 1961; Brinker et as follows: one posteroanterior, one anteroposterior, al., 1965; Kurze et al., 1965; Lapayowker and one each right and left laterals and subaxial Christen, 1965), and brain scanning (Cowan et (Towne's) views. The radiographs were read as al., 1970; Moreno and DeLand, 1971; O'Mara normal or abnormal. The borderline cases in which and Mozley, 1971; Scheinberg and Taylor, further views were suggested for clarification were 1971; Gilday and Reba, 1972), in the investiga- considered abnormal irrespective of the result of and diagnosis of intracranial space occupy- such views. tion were recorded with an well established. The results pro- The electroencephalograms ing lesions is 8-channel Grass electroencephalograph. Standard duced by each one of these techniques have been mono- and bipolar montages were obtained. compared with those obtained with neuroradio- Stroboscopic stimulation was always carried out and logical contrast studies as well as operative and hyperventilation when possible. For the purpose of necropsy findings (Wang et al., 1965; Decker our study the electroencephalograms were classified http://jnnp.bmj.com/ and Knott, 1972). as positive if a focal abnormality was found. Diffusely We undertook this study to determine if a abnormal tracings were considered negative unless given combination of these non-invasive pro- the electroencephalographer in his report suggested cedures would securely demonstrate or exclude the possibility of either a midline or a posterior an intracranial mass lesion. fossa lesion. The echoencephalograms were obtained with a Hoffrel ultrasonoscope, model 101. Echoencephalo- METHODS grams were regarded as normal when showing 2 mm on September 27, 2021 by guest. 2 mm was con- Over 800 patients suspected of harbouring an intra- or less midline shift. A shift above cranial mass lesion were investigated at the Mount sidered abnormal. Sinai Hospital, Toronto, Canada, during the period Isotope angiography and brain scanning were 1 January 1970 to 15 December 1972. obtained on a Nuclear Chicago Pho-Gamma Only the records of those patients who had scintillation camera. Anterior, posterior, both right and left lateral, and both right and left oblique views 1 Reprint requests: Dr P. Daniel Suberviola, Department of Neuro- were recorded immediately and two to three hours surgery, Ottawa General Hospital, 43 Bruyere Street, Ottawa, Ontario, Canada, KIN 5C8. later (delayed scan). In 20%0 of the cases vertex 52 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.38.1.52 on 1 January 1975. Downloaded from

Non-invasive screening for surgical intracranial lesions 53 views were also recorded. Asymmetrical perfusion as TABLE 3 well as a focal 'hot spot' on early or delayed scans FINAL DIAGNOSES OF 31 CASES IN GROUP C were considered abnormal. Diagnosis Cases RESULTS Cerebrovascular accident 10 Late onset epilepsy 9 The patients could be divided into four groups Cerebral atrophy 3 Hypertensive encephalopathy 1 according to result: Pseudotumor cerebri 1 Metastatic carcinoma without brain metastases 1 Progressive supranuclear palsy 1 GROUP A: TRUE POSITIVE In this group we Head injury (concussion) 1 Arteriovenous malformation of the scalp 1 included those patients in whom a space occupy- Not yet diagnosed 3 ing lesion was shown by the non-invasive in- vestigations. The existence of such a lesion was later confirmed by contrast studies and, in some cases, by operation and/or necropsy. GROUP D: FALSE NEGATIVE This group en- compasses those cases in which the preliminary GROUP B: TRUE NEGATIVE In this group all the investigations were negative but a mass lesion non-invasive investigations were negative. Fur- was later found with contrast studies. This was a ther investigation of these patients by neuro- hypothetical group but none of our patients fell radiological procedures failed to show any this abnormality. into category.

The final results are shown in Table 1. There Protected by copyright. were 17 cases in group A (I12%), 99 cases in TABLE 1 group B (67%), 31 cases in group C (210%), and CLASSIFICATION OF 147 CASES ACCORDING TO RESULTS none in group D. The overall accuracy of the OF NON-INVASIVE INVESTIGATION TECHNIQUE combined non-invasive techniques to confirm or deny the existence of a mass lesion was 79%0. The Group Cases reliability, however, was absolute in the sense (No.) (' ,) that, whenever all the non-invasive investiga- A (true positive) 17 12 tions were negative, all neuroradiological pro- B (true negative) 99 67 C (false positive) 31 21 cedures were also negative. Conversely, in the D (false negative) 0 0 cases with proved pathology, one or more of the screening procedures showed the lesion. In the group A series there were 12 tumours, two arteriovenous malformations, one subdural GROUP C: FALSE POSITIVE In the cases included haematoma, one cerebral abscess, and one here, one or more of the preliminary studies intracerebral haematoma (Table 2). The electro- http://jnnp.bmj.com/ suggested a space occupying lesion but their encephalogram and the brain scan localized the existence could not be demonstrated by a neuro- lesion in 13 cases each (76%) and the skull radiological investigation. radiographs, the blood flow study, and the echo- encephalogram in nine cases each (52%). In four cases, only one of the five non-invasive TABLE 2 studies was abnormal: the electroencephalo- gram in a temporal lobe haematoma; the skull on September 27, 2021 by guest. FINAL DIAGNOSES OF 17 CASES IN GROUP A radiographs in a craniopharyngioma; the brain scan in an astrocytoma grade III and the echo- Diagnosis Cases encephalogram in an astrocytoma grade IV. Tumour 12 Arteriovenous malformation 2 In two cases all the studies were abnormal: a Subdural haematoma 1 meningioma and an arteriovenous malformation. Intracerebral haematoma 1 Cerebral abscess I In the group C series there were 31 cases. The final diagnoses in these were cerebrovascular J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.38.1.52 on 1 January 1975. Downloaded from 54 P. Daniel Suberviola and N. David Greyson accident in 10, late onset epilepsy in nine, scan lessens the likelihood ofpresence oftumour cerebral atrophy in three, and one case each of to 5%o (Wang et al., 1965; Murphy et al., 1967; hypertensive encephalopathy, pseudotumor Decker and Knott, 1972). In 147 cases, the cerebri, metastatic carcinoma without cerebral combination of the results obtained by these involvement, progressive supranuclear palsy, procedures added to those of skull radiographs head injury, and arteriovenous malformation of and echoencephalography, effectively showed or the scalp (Table 3). Three cases could not be excluded the presence of a space occupying lesion securely diagnosed. in 79% of them. Furthermore, there were no The electroencephalogram gave most false false negative results and, therefore, no mass positive results, as it was abnormal in 24 out of lesion was missed. From this point of view, the 31 cases, and the only abnormality in 16. This reliability of the technique is 100%, which com- represents an overall of 16% false positive pares favourably with any of the neuroradio- results for electroencephalography in the series. logical investigations in current use. In a pre- The skull radiographs, isotope angiography, and vious study, in only two out of 44 histologically brain scan were falsely positive in six cases each, proven tumours reported by Wang et al. (1965) or 4% for the whole series. There were no false were the electroencephalogram, brain scan, and positives for echoencephalography. skull radiographs normal. It should be noted that in their study not all patients had all investigations. This, as well as the use of the less DISCUSSION sophisticated scanning techniques then available, The purpose of a screening test is to provide a may account for their false negative results. They rapid and simple means, with low morbidity, of also had a lower yield from echoencephalography Protected by copyright. separating those patients who require further (41% compared with 52%). We find it rather investigation from those in whom the probability interesting that in these same two cases angio- of undiagnosed pathology is low. The definitive graphy also gave negative results. methods of assessment of patients with intra- From our data we conclude that the applica- cranial mass lesions such as pneumoencephalo- tion of our technique, in the case of a negative graphy, cerebral angiography, and the like result, saves the patient the risks, however possess some inherent morbidity and occasional minimal, of the more elaborate neuroradio- mortality (Taveras and Wood, 1964; Fischer, logical studies, hospitalization time, and money. 1968; Abrams, 1971; Natelson et al., 1972; The latter consideration is most important in this iWhite et al., 1973). age of escalating cost in medical care. A total of The need for an effective screening system in 228 neuroradiological procedures was carried the investigation of patients suspected of having out in these 147 patients, 77 of them in groups A an intracranial space occupying lesion is obvious. and C and 151 in group B. In other words, 99 This is particularly true in otherwise asymptom- patients underwent 151 'unnecessary' procedures atic patients who are being investigated for and hospitalization. http://jnnp.bmj.com/ headaches, or in symptomatic patients in whom When we embarked on this study, our concern it is necessary to 'rule out' rather than confirm was for accuracy of exclusion rather than the presence of an operable mass lesion such as diagnosis of lesions. Many patients in our those suffering from late onset epilepsy, pseudo- original group of 800 who had an intracranial tumor cerebri, multiple sclerosis, etc. mass had to be excluded from the study. These Skull radiography, electroencephalography, were the cases with an echoencephalographic echoencephalography, and brain scanning are shift or a positive brain scan who went directly on September 27, 2021 by guest. now routinely used as screening procedures. to angiography or surgery and thus missed some They have the advantage of being possible to other of the non-invasive investigations. They carry out on an outpatient basis, on one short could have been added to group A on the basis of visit. The results are usually available within 24 a positive study alone. This would have in- hours. creased our apparent percentage of overall It has been shown previously that the com- accuracy. bination of a normal EEG with a normal brain The fact that there were 21% false positive J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.38.1.52 on 1 January 1975. Downloaded from

Non-invasive screening for surgical intracranial lesions 55

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Electroencephalography and Clinical Neuro- without a positive static image, was considered physiology, 33, 303-310. abnormal in our investigation, although cerebral Fischer, H. W. (1968). Hemodynamic reactions to angio- vascular insufficiency was correctly diagnosed or graphic media. A survey and commentary. Radiology, 91, an infarct could be recognized by assessing the 66-73. Gilday, D. L., and Reba, R. C. (1972). The role of brain appearance of the abnormal scan image. A scanning in the differential diagnosis of seizures. Canadian number of false positives requiring additional Medical Association Journal, 106, 1091, 1093-1094. investigation is preferable to missing a poten- Kurze, T., Dyck, P., and Barrows, H. S. (1965). Neurosurgical tially treatable intracranial mass. This is empha- evaluation of ultrasonic encephalograph. Journal ofNeuro- sized by the 32 cases with abnormal electro- surgery, 22, 437-440. Lapayowker, M. S., and Christen, G. E. (1965). 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56 P. Daniel Suberviola and N. David Greyson

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