1. Cung phan xa H.
Phan xa H (phan xa Hoffmann) la cung phan xa ddn synap (monosynaptic refflex): spi htfdng tam thuoc nhom spi la (co dUOng kmh ldn) xuat phat ttf thoi co cua cd dep, trung tam phai xa la khoanh tuy S i, sdi ly tam thuoc nhom sdi alpha co than te bao nam d sting trtfdc tuy chi phoi cho cd nay.
Hoffmann va sau do nhieu tac gia khac da dung dong dien mot chieu kich thich vao day than kinh chay tao nen cung phan xa va phat hien mot so" thtfdng ton cua he than kinh ngoai vi.
2. Ghi phan xa H.
Phan xa H la dap tfng do ki'ch thi'ch than kinh chay sau d ho"khoeo va ghi tai cd dep:
- Ki'ch thi'ch: xung vuong 0,5S ki'ch thi'ch day th in kinh chay sau. Ctfdng do ki'ch thi'ch tang dan ttf 0 den khi thu dtfdc dap tfng ctfc dai (H.max.).
- Ghi: dien ctfc be mat dat tai cd dep. Dien ctfc hoat dong dat tai diem gitfa dtfdng noi dinh ho" khoeo va diem gitfa bd sau mat ca trong. Dien ctfc trung tinh dat gitfa dien ctfc kich thich va dien ctfc ghi.
Hinh 2.4.: Dat dien ci/c ghi phan xa H.
De phan xa H co diidc dap ting to'i tfu: benh nhan hoan toan thoai mai va co the lam nghiem phap Jendrassik de han che tac dung tic che cua vo nao xuong khoanh tuy S,.
3. Cac thong so
- Thdi gian tiem tang cua dap ting M (LM): phan anh dan truyen ngon chi cua cac sdi van dong.
- Thdi gian tiem tang cua phan xa H (LH): la thdi gian tti khi ki'ch thi'ch den khi thu dUdc dap ting. No phan anh dan truyen trong cung phan xa H (bao gom sdi cam giac sau, trung tam phan xa, sdi van dong) la thong so giup danh gia dan truyen phan goc cua day th in kinh. Neu LM d gidi han binh thudng thi keo dai LH la thudng ton dan truyen (myelin) cac sdi cam giac sau
- Bien do cua dap ting M (AM): phan anh sdi true phan ngon cua cac sdi van dong
Bien do dap ting cua phan xa H (AH): phan anh tinh trang sdi true cac neuron tao nen cung phan xa H. Neu AM d gidi han binh thudng thi bat thudng AH noi len thUdng ton sdi true cac sdi cam giac sau.
4. Phan xa H binh thiidng
(Xem bang 2.3)
5. Phan xa H trong thiidng ton than kinh ngoai vi
0 Keo dai thdi gian tiem tang cua phan xa H
Bien do giam (thudng ton than kinh trung Udng thi phan xa H co tang bien do qua mtic lam chi so’ HAI >100% (do thoat tic che trung Udng cua phan xa H).
- Co the dung phan xa H de phan biet thudng ton re L5 va S 1 (thUdng ton L5 thi phan xa H khong thay doi)
•K
O benh nhan dai thao diidng, khi phan xa H co keo dai thdi gian tiem tang, bien do giam la bieu hien sdm cua bien chiing than kinh ngoai vi.
JK v
O cac benh than kinh ngoai vi do riidu, tang ure huySt, thay doi phan xa H la chi so" cho thay thudng ton than kinh cam giac d giai doan sdm.
BANG 2.3: MOT SO CHI SO DIEN SINH LY THAN KINH NGOAI VI BiNH THLTONG (THEO LE QUANG Cl/ONG CO SUA DOI). BiNH THLTONG (THEO LE QUANG Cl/ONG CO SUA DOI).
T K W Bien do (mV)
TGTT (m s)
TOOT (m/s) Chi so F (ms) Phan xa (n = 200)
TKchay chay 11,95 ± 5,74 4,75 ±0,71 / 46,42± ,26 12,15±1.49 LH (ms): 27,61 ± 1,58 AH (m V): 4,14 ±2,31 LM (mS): 4,52 ±0,66 AM (mV): 13,21 ± 5, 86 TK mac
6,38 ± 3,40 4,31 ±,0,70 51,87 ±6,53 13,42 ±1,52 Ghi chu - TGTT: thdi gian tiem tang. - TODT: toe (5o dan truyen.