脳脊髄液のHomovanillic acidと5—Hydroxyindoleacetic acid—脊髄液と脳室液間の濃度差および脳室液における変動

HOMOVANILLIC ACID AND 5-HYDROXY-INDOLEACETIC ACID IN THE CEREBROSPINAL FLUID OF MAN : CONCENTRATION GRADIENTS BETWEEN LUMBAR AND VENTRICULAR CSF AND VARIATIONS IN VENTRICULAR CSF

I．はじめに

　脳脊髄液のhomovanillic acid （HVA），5—hydroxy—indoleacetic acid （5—HIAA）は，おのおのdopamime（DA），5—hydroxytryptamine （5—HT）の代謝産物であり，これらを測定することにより各種脳疾患の病態を脳内アミン代謝の面より解明しようとする試みがなされている。脳脊髄液の採取部位としては，脳室，大槽，脊髄クモ膜下腔などが考えられるが，今日までの報告の多くは，主として腰椎穿刺により得られた脊髄液のHVA，5—HIAA値を分析することにより論じられている。しかしながら，HVA,5—HIAAの産生部位はおのおの異ること，および脳内アミンに日内変動がみられることなどから，髄液採取の部位と時間，髄液の通過障害の有無などによつてもその値は変動することが推測され，これらアミン代謝産物の測定意義に関しては未だ不明な点が多い。

　今回は，脊髄液と脳室液におけるHVA,5—HIAAの濃度差，pneumoencephalography （PEG）施行時の空気注入前後のHVA,5—HIAAの濃度差，および脳室液におけるHVA,5—HIAA濃度の日内変動の有無を検索し，あわせて脳脊髄液の通過障害によるHVA,5—HIAAレベルの変動について検討を加えた。

1. Concentration gradients of Homovanillic acid (HVA) and 5-Hydroxyindoleacetic acid (5-HIAA) between lumbar and ventricular cerebrospinal fluid (CSF): The concentrations of HVA and 5-HIAA in lumbar and ventricular CSF were measured in 8 cases with disturbance of CSF circulation. In all cases, ventricular CSF samples were obtained within a few days after collections of lumbar CSF. In 6 cases, ventricular CSF was taken through a drainage tube placed in the anterior horn of the lateral ventricle. In 2 cases, ventricular CSF was aspirated by puncture of the flushing device of the ventriculo-peritoneal shunt or Ommaya's reservoir connected to the tube which had been inserted into the ventricle. HVA was measured fluori-metrically with a modified method of Curzon et al. and 5-HIAA with the method of Ashcroft et al. respectively. Ventricular CSF values of HVA were significantly higher than lumbar CSF (P< 0.01), and concentration gradients were remarkable in cases with complete block of CSF flow. However, irrespective of site and degree of dis-turbance in CSF circulation, the 5-HIAA level of ventricular CSF did not differ from that of lumbar CSF.

2. HVA and 5-HIAA values in lumbar CSF before and after the injection of air during pneumo-encephalography (PEG): PEG was performed in patients without obstruction of CSF flow. The first sample was taken immediately after the spinal tap, and the second sample was obtained at the end of the procedure, after 20-40 ml of the air had been injected. HVA and 5-HIAA concen-trations in CSF were measured in 12 and 19 cases respectively. Both HVA and 5-HIAA values of the first samples did not differ significantly from those in lumbar CSF from patients without neuro-logical disease. HVA values of the second samples were significantly higher than those of the first samples (P<0.001). On the contrary, 5-HIAA did not rise after the injection of air.

3. Variations of HVA and 5-HIAA in ventricular CSF: Ventricular CSF was obtained through a drainage tube placed in the anterior horn of the lateral ventricle in 10 patients, 8 cases of brain tumor and 2 cases of cerebrovascular disease. CSF samples were drained every 4 hours in 2 cases, 3 hours in 2 cases, and 2 hours in the other casesfor 1-4 days.

The HVA and 5-HIAA values varied with time in all the cases. Significant and high correlations were found between ventricular HVA and 5-HIAA levels in 6 cases. The relationship was not observed between variations of HVA and 5-HIAA and rhythm of sleep and arousal.

In a patient with brainstem hemorrhage, both HVA and 5-HIAA values were low. Both HVA and 5-HIAA concentrations varied at high levels in 2 cases with complete block of CSF flow, a case with pineal tumor which involved the aqueduct of Sylvius, and a case with ependymoma which filled the fourth ventricle. However, in a case with craniopharyngioma in the third ventricle which blocked the bilateral foramina of Monro, 5-HIAA values were not so high while HVA varied at high levels. Our data may suggest that ventricular CSF 5-HIAA derives from the upper level than the aqueduct of Sylvius and presumably originates from the periventricular structure of the third ventricle.

It may be seemed that estimation of HVA and 5-HIAA concentrations in CSF is valuable tool to investigate the brain monoamine metabolism. However, many factors must be considered in the interpretation of results in clinical studies.