Ve ban chat phan xa nhay mat (blink reflex) giong nhu phan xa giac mac nhung dUdc phan ti'ch dinh ludng chi'nh xac tren may tU dong phan ti'ch ket qua.
Phan xa nhay mat giup danh gia dtfdc c h ic nang hoat dong cua day V, day VII, cac neuron trung gian va trung tam phan xa d vung than nao.
1. Cd che phan xa nhay mat
r 1 R2 cung ben
Hinh 2.10: Dtfdng ghi dien hinh cua phan xa nhay m lt sau kich thich d mot ben gom mot dap ufng R1 d cung ben va hai dap Lfng R2 dong
thdi d hai ben.
Thdi gian tiem cua dap i n g phan xa R l la L l, R2 cung ben la L2, R2 doi ben la L3, bien do R l, b la bien do trung binh cua R2 cung ben, c la bien do trung binh cua R2 doi ben.
Phan xa nhay mat (blink reflex) gom hai dap vfng: - Dap iing R l la phan xa ddn synap: neuron htfdng tam la day V, neuron trung gian nlm d cau nao cd nhiem vu tiep noi neuron htfdng tam vdi neuron ly tam (la day VII) cung ben.
- Dap i n g R2 la phan xa da synap: neuron htfdng tam la day V, neuron trung gian n&m d cau nao va hanh nao cd nhiem vu tiep noi neuron htfdng tam vdi neuron ly tam (la day VII) d cung ben va doi ben (khi kich thich htfdng tam, dien vao nhanh tren o mat cua day V mot ben se ghi dtfdc R2 d ca hai ben)
2. Phan xa nhay mat binh thifdng
Theo Kimura J. (1983) phan xa nhay m it cua ngtfdi binh thudng la:
Thdi gian tiem cua R l = 10,5 ± 0,8ms (L l)
Thdi gian tiem cua R2 cung ben = 30,5 ± 3,4ms (L2) Thdi gian tiem cua R2 doi ben = 30,5 ± 4,4 ms (L3).
3. Phan xa nhay mat benh ly
Thdi gian tiem R l trong nhiing benh mat myelin cua than kinh ngoai vi (day V, day VII) hoac trung Udng (u ho so sau) do de ep day than kinh hay benh ly d than nao:
R l thay doi khong nhat thiet do qua trinh benh ly cua chinh cung phan xa ma con co the do phu ne hoac do thudng ton d ngoai cung phan xa (vi du than nao bi tic che do hon me, tai bien mach mau nao...)- NhUng khi dUdc hoat hoa day du (kich thich ngat quang vdi thdi gian 3 - 5ms giUa cac kich thich) thi thdi gian tiem cua R l the hien dan truyen cua chinh cung phan xa.
R2 thay doi cd the do thudng ton trUc tiep con dudng phan xa nhu trong hoi chUng Wallenberg hoac do nhutng thudng ton gian tiep anh hudng den tinh chiu kich thich cua synap lien hdp.
4. Phan xa nhay mat trong liet day VIII ngoai vi
- R l bi giam hoac mat d ben liet.
- R2 bi giam hoac mat d ben liet (khong ke kich thich ben nao)
- La phudng phap tot nhat de xac dinh liet day VII
ngoai vi d miic do rat nhe (Diagne. M va cs (1989).
- Danh gia tien ltfdng kha nang hoi phuc trong liet day VII ngoai vi d giai doan sdm (trong vai tuan dau): dung phan xa nhay mat ket hpp vdi kich thich trtfc tiep day VII, neu thay R l va R2 trtfdc day mat nay lai xuat hien trd lai thi thuyen giam se xuat hien vai thang sau khi bi benh (Kimura J., 1993).
Phan xa nhay mat tot thi hoi phuc tot (Heal JP.,1988).
Theo Ghonim MR., Gavilan C. (1990), benh nhan cd phan xa nhay mat binh thtfdng thi 93,7% hoi phuc tot, cham R l thi 86,8% hoi phuc, mat phan xa nham mat thi 55,8% hoi phuc.
5. Phan biet thtfdng ton de ep day V vdi dau day V
ttf phat
Thdi gian tiem cua phan xa nhay mat chi bi anh htfdng khi thtfOng ton de ep day V cdn trong dau day V ttf phat thi khong bi anh htfdng.