J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.31.3.245 on 1 June 1968. Downloaded from J. Neurol. Neurosurg. Psychiat., 1968, 31, 245-249 A-scan echoencephalography in measurement of the cerebral ventricles ANAND G. GARG AND ALEX. R. TAYLOR From the Department ofNeurological Surgery, Royal Victoria Hospital, Belfast, Northern Ireland The first attempts at ultrasonic visualization of the METHOD cerebral ventricles were made by Dussik (1948), The ventricular measurements obtained at echoen- Ballantine, Ludwig, Bolt, and Hueter (1950), and cephalography were compared with the x-ray measure- Hueter and Bolt (1951), using the transmission ments made at pneumoencephalography. method. The possible use of the pulse-echo method ANATOMICAL CONSIDERATIONS The third and lateral (echoencephalography) for the diagnosis of hy- ventricles are supratentorial structures. The third ventricle lies between the two thalmi, communicating drocephalus was suggested by Leksell (1956). Later in front with the lateral ventricles through the inter- Kikuchi, Uchida, Tanaka, and Wagai (1957) and de ventricular foramina and behind with the aqueduct of Vlieger and Ridder (1959) recorded echoes from the the midbrain. The septum lucidum and the third ventricle walls of the lateral ventricles. According to Gordon lie in the central plane of the brain. Protected by copyright. (1959), and de Vlieger and Ridder (1959), the width The lateral ventricle is a C-shaped cavity lying within of the third ventricle can also be measured. ter the cerebral hemisphere. It consists of a central body and Braak, Crezde, Grandia, and de Vleger (1961) used three horns-anterior, posterior, and temporal-running pneumoencephalography to study the origin of into the frontal, occipital, and temporal lobes respec- ventricular echoes. Lithander (1961a) investigating tively. hydrocephalus in children, thought that the lateral The ventricular system on the two sides is normally symmetrical about a central plane. The ventricles may ventricular size could be measured with relative be distorted or asymmetrical, because of hydrocephalus certainty and also confirmed the value of the tech- or any space-occupying lesion. nique in outlining an enlarged third ventricle. Ambrose (1963, 1964) expressed the width of RADIOGRAPHIC CONSIDERATIONS At pneumoencephalo- the lateral ventricles, obtained at echoencephalo- graphy, with the patient lying supine, the bodies of the graphy, as a fraction of the distance from the lateral ventricles are shown in the antero-posterior radiograph as two triangles lying one on either side of the midline echo to inner skull table. A ratio of one- midline. Each triangle has a supero-medial, supero- fifth to one-sixth was considered normal, of lateral, and inferior angle. Joined to the triangles is a one-quarter a slight dilatation, of one-third mod- fainter shadow of the anterior horns. Between the two erate dilatation, and of half or more as gross inferior angles lies the superior part of the third ventricle http://jnnp.bmj.com/ dilatation. Russo and Arnold (1964), and Dreese and extending downwards for nearly 1 to 1 5 cm. Netsky (1964) also reported on the diagnosis of hy- To obtain perfect antero-posterior projection, the drocephalus. Schiefer and Kazner (1966) assessed patient lies supine with the skull base line at 900 to the the thickness of the remaining cerebral layer in film and 90° to the table. The centre pointer is 3-8 cm infantile hydrocephalus from the lateral ventricle above the level of the nasion, directed at the centre of the echoes. Umbach and Kley (1965) reported on the diag- grid. nosis and the control of progress by serial echo- ULTRASONIC CONSIDERATIONS The shape of the ven- encephalograms in 75 children with hydrocephalus. tricular system varies at different levels, and the distance on September 27, 2021 by guest. Jacobi and Stephan (1965) detected a dilated third from the lateral walls of the lateral ventricles to the mid- ventricle in 305 patients. Lapayowker and Christen sagittal plane of the skull varies correspondingly. This (1965), in 66 makes it difficult to standardize the measurement of patients, obtained lateral ventricle ventricles for different degrees of dilatation by echoence- echoes, 1-4 to 2-2 cm from the midline, corres- phalography. Moreover, the normal limits of the ven- ponding to the posterior portion of the lateral tricular system are uncertain. It is thus essential to know ventricles. Kessler (1965) and Gordon (1966), on which part of the ventricular system lies in the path of the other hand, do not think that these echoes are the ultrasonic beam. a reliable indicator of ventricle size. Because ofthe differences in specific acoustic impedance 245 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.31.3.245 on 1 June 1968. Downloaded from 246 Anand G. Garg and Alex. R. Taylor of the cerebral tissue and the cerebrospinal fluid (1-59 and 1 51 x 106 g/cm2/sec respectively, according to Kazner, Kunze, and Schiefer, 1965), echoes are given from both, walls of the third ventricle and the septum lucidum (the midline echo) and the lateral walls of the lateral ventricles (the ventricular echo). The part of the record, between the midline echo and the ventricular echo is almost echo free. The width of the midline echo is the width ofthe third ventricle. A Siemen's Echoencephalograph USM I was used, equipped with a polaroid camera. The best ventricular echoes were obtained from a crystal position 025 to 0 5 cm above the tip of the ear. The ultrasonic beam. must be narrow and non-divergent. It is parallel in the Fresnel zone (near-field) after which it diverges. As the length of Fresnel zone and the angle-of-divergence are dependent on the frequency and diameter of the crystal (which are themselves interdependent), the selection of crystal size is critical. According to the manufacturers the beam in the Fresnel zone, in practice, is not absolutely FIG. 1. Steinmann pin through a burrhole along the path parallel but is bundled just before its end. Consequently, ofultrasonic beam. there is a slight increase in power, which is desirable be- cause of attenuation. If the diameter and frequency of the investigated for posterior fossa lesions, three for hydro- crystal are chosen, so that this bundling takes place in the cephalus, and the remaining 45 for supratentorial lesions. region of the particular structure examined, more prominent echoes are received. A barium-titanate RESULTS crystal of 15 mm diameter was employed, pulsing at a Protected by copyright. frequency of 2 Mc/sec. It has a Fresnel zone of 7 5 cm With the help of a neuroradiologist the ventri- and an angle-of-divergence of 3°30'. The crystal has a cular appearance, in terms of its apparent size, pulse repetition rate of 430 pulses/sec and each pulse lasts was classified into five grades: normal (up to 7 mm), for I,sec. It is applied at symmetrical positions on minimal dilatation (8-10 mm), slight dilatation either side of the head. (11-13 mm), moderate dilatation (14-17 mm), To find out the exact site of the ventricular system and gross dilatation (above 18 mm). The figures in traversed by the ultrasonic beam, as seen in an antero- parentheses represent the measurements made at posterior radiograph, the following study was done on a cadaver. Air was injected into the ventricle through a the inferior angle after the degree of dilatation was right frontal burrhole. Another small burrhole was made assessed. in the skull, at the position used for ventricular measure- Echo and pneumoencephalographic measurements ment by echoencephalography. A 6-mm wide Steinmann were found in complete agreement for the right pin was introduced perpendicularly, through this burrhole, lateral ventricle in 19 patients and the left lateral along the presumed path of the ultrasonic beam. A ventricle in 28 (Table I). radiograph taken after this demonstrated the pin passing through the inferior angles of the body of the lateral TABLE I ventricles and the upper part of the third ventricle DIFFERENCE IN ECHO AND X-RAY MEASUREMENTS http://jnnp.bmj.com/ (Fig. 1). Difference of measurement Patients (no.) Measurements at echoencephalography were made (mm) from the centre of the midline echo to the rising flank right side left side of the ventricular echo. Measurements were made on Echo > x-ray radiographs, of the inferior angle of the body of the 1 11 9 ventricles on a level with the upper part of the third 2 13 6 ventricle, from the midline to the lateral wall. 3 3 3 4 5 1 MATERIAL 6 on September 27, 2021 by guest. Eighty-seven patients were examined by echoencephalo- Echo < x-ray 1 12 13 graphy and pneumoencephalography in that order. Of 2 10 9 these, nine were discarded-because of poor ventricular 3 4 filling in four and unsatisfactory radiographs in five. 4 3 5 Of the remaining 78, nine were below 10 years, six 6 1 2 between 10 and 15 years, and 63 were adults. Of the total patients, 10 were admitted with Parkinson's disease, 20 Tota I 59 50 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.31.3.245 on 1 June 1968. Downloaded from A-scan echoencephalography 247 Analysing the results for both the ventricles obtained in differentiating between the normal together, correct results were obtained in eight ventricles and minimal dilatation, and between the patients, a difference up to 1 mm on either side in iinimal and the slight dilatation. In no patient was 21 patients, difference of between 1 and 2 mm in a ventricular dilatation missed, the mistakes being six patients, difference of 2 mm on either side made only in correct grading of the dilatation. in 19 patients, and difference of more than 2 mm On the basis of our series, the following table of on either side in 24 patients.