Tentorial dural arteriovenous fistulae are rare clinically.是什么意思？

Tentorial dural arteriovenous fistulae are rare clinically.

小脑幕脑膜动静脉瘘临床上比较少见.

dural

adj. 硬脑膜的，硬脊膜的；

例句
The treatment dural arteriovenous fistula are still controversial now.
对小脑幕动静脉瘘的治疗目前仍存在很多争论.

arteriovenous

adj. 动静脉的，连接动静脉的；

例句
It was concluded that there were arteriovenous anastomosis in yak's heart.
牦牛心室肌中存在着动静脉吻合.

fistulae

n. 管状器官，漏管，瘘，瘘管( fistula的名词复数 )；

例句
With colonic involvement, perirectal fistulae are common.
累及结肠的直肠周瘘管常见.

are

vi. （用于第二人称单复数现在时，第一、三人称复数现在时）是；n. 公亩（等于100平方米）；

例句
We are scared to abandon ourselves to our feelings in case we seem weak or out of control.
我们不敢放纵自己的情感，以免显得太过软弱或缺乏自制。

rare

adj. 罕见的，特殊的，半熟的；半生的，稀薄的，经过稀化的，三分熟；

例句
It was one of his rare attempts at humour.
那是他极不常见的想要表现幽默的一次。

clinically

adv. 冷静地，客观地；

例句
Leaving aside the tiny minority who are clinically depressed, most people who have bad moods also have very good moods...
撇开极少数临床抑郁症患者不谈，大多数情绪低落的人也有心情非常愉快的时候。