小頭症の髄液循環動態の研究—特にRI cisternographyおよびRI ventricular clearanceによる検討

A STUDY ON CSF DYNAMICS OF THE MICROCEPHALY: ADIOISOTOPE CISTERNOGRAPHY AND RADIOISOTOPE VENTRICULAR CLEARANCE

I．はじめに

　小頭症microcephalyとは頭蓋が狭少な状態を意味するが，一般には狭頭症は除かれる。したがつて頭蓋が小さいが，骨縫合の早期癒合がなく，また頭蓋内圧亢進も伴わないものを指す。

　小頭症は一次的発育異常genetic （primary microce—phaly）（以後G．　M．とする）と胎生後期以後種々の外因性障害が加わつて生じたと考えられる二次性発育障害secondary （acquired microcephaly）以後（S．M．とする）とに分類できる。

The purpose of this paper is to evaluate the RI cisternography and RI ventricular clearance in the study of CSF flow in microcephaly. The micro-cephalies were classified into a genetic (primary) and a secondary (acquired) types according to family history, developmental history and present status, ⁱn particular to early history including prenatal, perinatal and postnatal history.

In these microcephalic children CSF dynamics were investigated by means of RI cisternography and RI ventricular clearance.

Results :

1. 23 of 37 microcephalies were of secondary type including 10 cases of asphyxia (livida and pallida) during perinatal periods, 2 cases of subdural effusion and one case of subdural hematoma.

2. The head circumference of all the cases was below the value of standard deviation of normal head growth presented by Nellhaus. Any difference of head size was not recognized between the genetic and the secondary microcephalies.

3. In 21 of 37 cases, RI cisternography were performed and remarkable malabsorption was show-ed in only 3 cases, and the reflux into the lateral ventricles was recognized in only 4 cases. However, abnormal asymmetric cisternograms were detected in 10 cases (consisted of 9 secondary microcephalies and one genetic microcephaly), and pathologic find-ings were a localized increased RI concentration in some cases and a decreased RI concentration in other cases. The correlation between an asymmetricRI concentration in cisternography and an asym-metric abnormal finding in pneumoencephalogram was not recognized. Asymmetric cisternograms did not related with asymmetry of the skull.

4. The examination of RI ventricular clearance was carried out in 12 microcephalies (5 genetic and 7 secondary types). The procedure was as follow-ings : The patients being anesthetized by intra-muscular injection of Ketamine® were fixed on supine position. Two hundreds μCi of ¹⁶⁹Yb-DTPA was injected percutaneously into the anterior horn of the lateral ventricle through a burr hole, which had been opened before the examination. RI counts on the head were recorded with Anger-camera tape-recorder for one hour in lateral view. Playing back the tape, the region of interest (ROI) was settled in the anterior horn of lateral ventricle and in the cisterna magna with an image scope, and the changes of RI activity in each region were displayed on the two pen-type recorder with rate-meter. This clearance curve of the ventricle simu-lated an exponential curve or almost straight line. The half-time, which means a time taken from the initial peak in activity on CSF clearance curve to 50% activity of the initial peak, is called as "di-ffusion rate" in this study for convenience. The half time of normal children was 20 to 25 minutes.

5. In 7 secondary microcephalies out of 12 micro-cephalies, half time revealed more than 25 minutes without exceptionally, was exactly distinguishable from the normal levels and involved 5 delayed CSF flows which were showed in slower levels than 50 minutes of the half time. In the remained 5 genetic microcephalies, the half time revealed less than 25 minutes. The half time of ventricular clearance curve was not found to relate to the cir-cumference of head, Evans ratio and CSF pressure.

6. Therefore, radio-isotope ventricular clearance seemed to be suitable as the detector for the CSF dynamics, which means CSF circulation mainly from the choroid plexus to the subarachnoid space and ventricular CSF diffusion.

7. The abnormal asymmetric findings of RI cis-ternography and the measurement of RI ventri-cular clearance supplied an available information for disturbance of CSF dynamics in microcephaly.

Therefore these procedure can be said to be an useful parameter to classify to type of microcephaly.