Magnetic Resonance Imaging (MRI) in Syringomyelia

Transcription

1 Act Neurochir (Wien)(1995) 134:93-99 :Act. _ N urochlrurgc 9 Springer-Verlg t995 Printed in Austri Mgnetic Resonnce Imging (MRI) in Syringomyeli H. L. J. Tnghe Deprtment of Rdiodignostics, University Hospitl Dijkzigt, Rotterdm, The Netherlnds Summry Bsed on n own mteril of 19 ptients with syringomyeli nd on the relted literture survey is given on the dignosis, differentil dignosis, postopertive evlution nd the dynmics of CSF nd cyst fluids, using mgnetic resonnce imging (MRI). The following conclusions cn e drwn: l. MRI is the preferred method of investigtion for dignosis nd differentil dignosis of syringomyeli. 2. Using MRI, it is possile to study fluid flow in the verterl cnl nd the movements of the syrinx fluid. The dt re s yet limited, ut in the future will form n importnt contriution to our understnding of the pthogenesis of syringomyeli nd to the choice of tretment method. 3. MRI is importnt for the postopertive follow-up of ptients with syringomyeli, including trcking the cyst nd detecting complictions. Keywords: Syringomyeli; mgnetic resonnce imging; MRI. 3. Determintion of sept in the cysts (Fig. 2). 4. Detection of ssocited disorders, such s cysts in the posterior foss (Fig. 11 nd ), tethered cord, Chiri mlformtion etc. (Fig. 3). 5. Follow-up fter tretment nd detecting complictions of tretment. 6. Study of fluid motion in the surchnoid spce nd in the cyst using flow imging techniques. Mterils nd Methods This rticle is derived from the results of MRI (nd other) exmintions in 19 ptients, in whom the dignosis of syringomye- Introduction Since the dvent of mgnetic resonnce imging intrmedullry normlities cn e directly visulized. In this pper we descried MRI findings in syringomyeli in generl nd the fluid motion in the syrinx cyst on phse shift imging in prticulr. The clinicl significnce of this technique is demonstrted in series of 15 ptients. MRI in Syringomyeli Mgnetic resonnce imging (MRI) is the most importnt neurordiologicl method of investigtion for suspected syringomyeli [2, 7, 8]. The dvntges of MRI include [1, 2, 8-11]: 1. Demonstrtion of syrinx cyst in norml sized, or trophic spinl cord, especilly in cses of post-trumtic syringomyeli (Fig. 1). 2. Determintion of the lower nd upper orders of the cyst. Fig. 1. Syrinx cyst in spinl cord without enlrgement (T1W imge)

2 94 H. L. J. Tnghe: Mgnetic Resonnce Imging (MRI) in Syringomyeli sidered: the size of the cyst, the size of the spinl cord, sept in the cyst, the fluid motion on non-quntittive phse-shift imging, the ntomicl condition fter formen mgnum decompression, the ssocited normlities, the evolution fter tretment, nd the position of possile syringo-surchnoid shunt. Fig. 2. Syrinx cyst with multiple sept (TlW imge) Results MRI filed to demonstrte syrinx cyst in 4 of 19 ptients. Two of these ptients hd no normlities, one hd Chiri mlformtion without cyst, nd one ptient hd n trophic cervicl spinl cord without cyst. Eleven of the 19 ptients hd n ssocited Chiri type I mlformtion nd one ptient hd Chiri type II mlformtion. There ws one cse of syringomyeli of the distl spinl cord in the context of tethered cord with thickened filum terminle nd scrl extrdurl rchnoid cyst. Two ptients hd syringomyeli without ssocited normlity. Ptients with post-trumtic syringomyeli hve not een included in this study, lthough such cses were investigted during the period [3]. The Bsic Fetures of Syringomyeli Syringomyeli hs two sic fetures on MRI: 1. The presence of cyst in the spinl cord prenchym. 2. The ssocited norml signl of the spinl cord due to gliosis. This second feture ws not further investigted in our protocol. These fetures cn e nlysed in the Tl-weighted imge (TIW imge) nd in the T2-weighted imge (T2W imge). The T1W imge [8]: The sgittl T1W spin echo sequence is the sic sequence in every MRI investigtion of the verterl column nd its contents. The Fig. 3. Syringomyeli of the distl spinl cord in ptient with tethered cord. Also thickened filum terminle nd scrl extrdurl rchnoid cyst (not shown) (TlW imge) li ws estlished on the sis of clinicl neurologicl exmintion nd previous neurordiologicl investigtions. The MRI exmintions were performed ccording to fixed protocol during the period Decemer Septemer When ssessing the results, the following prmeters were con- Fig. 4. () In smll non-pulstile syrinx cyst the signl intensity is higher thn the pulstile CSF (TlW imge). () In lrge syrinx cyst the signl intensity is equl to CSF (TlW imge). Sttus fter formen mgnum decompression

3 H. L. J. Tnghe: Mgnetic Resonnce Imging (MRI) in Syringomyeli 95 Fig. 6. Different signl intensities in the vrious comprtments of syrinx cyst with sept. () T1W imge (left), () PDW imge (right) Fig. 5. Fluid motion in the syrinx cyst cuses hypo-intense signl (signl void) in the non-flow compensted T2W imge T1W imge is prticnlrly suitle for imging norml ntomy nd for disorders which re chrcterized y distured ntomy such s syringomyeli. The syrinx cyst hs signl intensity equl to or slightly higher thn CSF, depending on the fluid motion. Smll cysts with sttionry fluid hve slightly higher signl intensity thn the pulsting CSF. Lrger cysts with pulsting fluid hve signl intensity similr to CSF (Fig. 4 nd ). The size of the cysts is very vrile nd cn rnge from smll focl cyst, s in post-trumtic syringomyeli, to cyst which stretches from the crnio-cervicl trnsition to the conus. The T1W imge produces more ccurte reflection of cyst size thn the T2W imge, ecuse it is less sensitive to flow effects. Sept in the cyst cn est e seen in the T1W imge. The T2W imge [8]: The T2W imge is prticulrly suitle for imging pthologicl tissue chrcterized y n norml signl intensity nd for investigting fluid dynmics. In multi-echo sequence we otin two imges with long TR: the proton density imge (PDW imge) with short TE nd the "hevy T2W imge" with long TE. Ech hs its own dignostic vlue. In the non-flow compensted T2W, pulstile fluid gives hypo-intense signl (signl void). This is lso produced y fluid motion in the syrinx cyst (Fig. 5). In syrinx cyst with severl sept it is Fig. 7. Myelomlci: onorml signl of spinl cord tissue ove the syrinx cyst possile tht the vrious comprtments hve different signl intensities due to differences in fluid motion (Fig. 6 nd ). The spinl cord tissue round syrinx cyst is often norml, giving hyper-intense signl. We use descriptive term for this tissue: myelomlci (Fig. 7). Distinction etween the sttic hyper-intense fluid of syrinx cyst nd myelomlci

4 96 H.L.J. Tnghe: Mgnetic Resonnce Imging (MRI) in Syringomyeli it Fig. 8. () Equl signl intensity in syrinx cyst nd djcent surchnoidl spce (TIW imge). () The pulstion in the syrinx is in close hrmony with tht in the djcent surchnoidl spce (phse-shift) It Fig. 9. () Phse-shift imging corresponds with crnio-cudl motion. () Phse-shift imging during CSF distole. White signl in the syrinx cyst corresponds with cudo-crnil motion my e difficult in the hevy T2W imge. In the PDW imge, myelomlci is hyper-intense. The Study of Syringel Fluid Motion In our series of 15 ptients, the fluid motion in the syrinx cyst ws investigted qulittively using non-flow compensted T2 spin echo sequence nd y phse-shift imging. The correltion with the clinicl condition ws investigted. Studies on the pulstile nture of the cervicl CSF were performed in 1966 y Du Bouly. These oservtions were extended y Lne nd Kricheff in 1972

5 H. L. J. Tnghe: Mgnetic Resonnce Imging (MRI) in Syringomyeli 97 using video densitometry nd lipiodol myelogrphy. CSF-pulstions in the spinl cnl were first descried on MRI y Shermn in t986. In 1988, Ruin nd Enzmnn were the first to use n MR method for quntifiction of CSF flow. Quencer nd Post descried the technique of phsecontrst cine MR in MR methods [4, 9-11] for the qulittive study of fluid movement re non-flow compensted T2W imge nd phse-shift imging. Quntittive MR methods re phse-contrst cine MR nd dul flip ngle technique [5, 8, 9]. The methods of non-motion-compensted T2W sequence hve threshold for the detection of fluid movement. This leds to type of inry phenomenon: with movement/without movement. And so this method is relly more qulittive thn quntittive. It is only quntittive insmuch s prticulr pulse-mplitude threshold hs to e exceeded. The phse contrst cine MR technique, in series of e.g. 16 imges spred over the entire period of hert et cycle, produces dynmic informtion out the speed nd direction of the fluid movement in the norml surchnoid spce nd in the syrinx. Two fetures of the fluid motion cn e nlysed: the speed (in mm/sec) nd the direction. The coding of the direction is such tht crnio-cudl flow is represented s lck signl, nd cudo-crnil flow s white signl. Asence of flow produces grey signl [9-11]. The quntittive MR technique for studying fluid motion is still in its infncy. It is not yet known how this informtion is correlted with the clinicl symptomtology, the progressive of the disese or the response to tretment. Just s little is known out whether there is reltionship etween the severity of djcent spinl column dmge (myelomlci) nd the dynmics of the movement. Dt known so fr: 1. The fluid motion in the syrinx cyst is pulstile in nture. 2. The pulstion in the syrinx runs in close hrmony with tht in the djcent surchnoidl spce (Fig. 8). 3. The fluid movement in the syrinx hs definite systolic nd distolic component, which run in prllel with those of the djcent surchnoidl spce. 4. The systolic component is imed crnio-cudlly; it is seen in the lst prt of the hert et cycle on the peripherl pulse metre recording, not on the ECG (Fig. 9 ). 5. The direction of the distolic component is cudo-crnil nd it lsts longer thn the systolic component (Fig. 9 ). 6. Lrge syrinx cysts hve pulstile wve which runs in systole from cervicl to thorcic nd the other wy round in distole. In generl, this pulstile wve Fig. 10. (, ) Non-uniform fluid motion in syrinx cyst with sept. Phse-shift imging () shows different signl intensity in the vrious comprtments of the syrinx cyst () Fig. 11. () Syrinx cyst efore tretment. Arnold-chiri type II mlformtion. () Diminution of the size of the cyst fter tretment of coexisting hydrocephlus. Arnold-Chiri type II mlformtion

6 98 H.L.J. Tnghe: Mgnetic Resonnce Imging (MRI) in Syringomyeli Fig. 12. Myelomlci in ptient with prplegi fter cervicl trum with terdrop frcture. () Hyperintense intrmedullry lesion on T2W imge in the xil nd () sgittl plne runs synchronously with the pulstile wve of the surrounding surchnoidl spce. 7. The fluid movement in the syrinx cyst is reltively uniform, ut turulence cn occur ner sept (Fig. 10.). 8. Postopertively, the fluid movement often decreses in proportion to the reduction in size of the cyst. In cyst which hs lmost collpsed, the fluid ecomes sttionry [8]. MRI in Postopertive Syringomyeli In our series, MRI ws crried out in ten ptients in the postopertive phse, in two ptients oth pre- nd postopertively nd in three ptients only pre-opertively. We looked t: 1. The ntomicl condition of the crnio-cervicl trnsition fter formen mgnum decompression, nd possile complictions; 2. The cyst size nd fluid movement; 3. The position of possile shunt ctheter. Usully, it ws impossile to imge the shunt ctheter ecuse of locl metl rtefcts. The MRI criterion for "successful" tretment is the diminution of the cyst (Fig. 11 ). It is not cler whether the syringel fluid motion lso hs to decrese. In series of 20 postopertive ptients of Brkovich [2], signl void remined in the cyst in ten ptients, without clinicl deteriortion t followup of one yer (possily too short). But in ll seven ptients in whom the cyst ws diminished, the syringel fluid motion lso decresed nd the numer of ptients with signl void in the cyst ws lrger preopertively (11/12 ptients) [2]. Fig. 13. Spinl cord tumour with cyst. () Gdolinium enhnced TlW imge of the tumour (left). () Fluid in tumour cyst hs higher signl intensity due to higher protein concentrtion (right) Differentil Dignosis The trunction rtefct: The "overdignosis of syringomyeli" stemming from the first dys of MRI, cn e lmed on confusion with the trunction rtefct. This rtefct is direct consequence of using the Fourier trnsformtion to crete n imge. In the cervicl spinl cord, this cn produce hypo-intense line in the centre. This nd is, however, never s hypointense s the signl produced y CSF [6]. Myelomlci: Lte progression of the neurologicl sequele following spinl trum cn e due to cuses other thn syringomyeli. For exmple: hypertrophy of the posterior longitudinl ligment, posttrumtic spondylosis deformns with osteophyte formtion, trumtic disc prolpse, rchnoiditis, "tethering" of the signl cord, post-trumtic intrdurl rchnoidl cyst with spinl compression nd myelomlci. They re ll visile on MRI. Myelomlci (softening of the spinl cord) is descriptive term. The neuropthologicl sustrte is comintin of neuronl loss, demyeliniztion, infrct nd gliosis. There my e ccompnying microsysts [7]. On MRI, these cn e confused with syrinx cyst: hypo-intense on the T1W imge, hyper-intense on the T2W imge. But zone of myelomlci is hyper-intense on the PDW imge, while the syrinx cyst looks the sme s CSF [7] (Fig. 12, ).

7 H. L. J. Tnghe: Mgnetic Resonnce Imging (MRI) in Syringomyeli 99 Spinl coi'd tumour with cyst (Fig. 13, ): On the T1W imge the differentil dignosis etween syringomyeli nd lrge tumour cyst cn e difficult. Zones of spinl cord swelling without cyst re indictive of tumour. The fluid in tumour cyst often hs higher signl intensity due to higher protein concentrtion mongst other things. On the T2W imge, oth tumour cyst nd syrinx cyst re hyper-intense. Inhomogeneous signl intensity (e.g. due to previous leeding) nd hyper-intense signl outside the cystic zone, ecuse of spinl cord edem or tumour tissue (minly on the T1W imge), indicte tumour. The MR-contrst gent, Gdolinium = DTPA, fcilittes differentition. A syrinx cyst does not stin while, ccording to current experience, ll spinl tumours do stin. Accompnying normlities of the crnio-cervicl trnsition nd cyst in occult spinl dysrphism mke spinl tumour highly improle. References 1. Bnn M (t989) Syringomyeli in ssocitin with posterior foss cyst. AJNR 9: Brkovieh AJ, Shermn JL, Citrin, et l (1987) MR of postopertive syringomyeli. 8: Btzdorf U (1991) Clssifiction of syringomyeli. In: Btzdorf U (ed) Syringomyeli. Willim nd Wilkins, Bltimore 4. Brdley WG, Nitz W (1991) CSF velocity imging in the spine. In: Hsso, Strk (eds) Ctegoricl course sylluss: spine nd ody MRI of Americn R6ntgen Ry Society, 90th Annul Meeting, 5-10 My, Cstillo M, Quencer RM, Green BA, et l (1987) Syringomyeli s consequence of compressive extrmedulry lesions: postopertive, clinicl nd rdiologicl mnifesttions. ANJR 8: Czervionke LF, Czervionke JM, Dniels, et l (1988) Chrcteristic fetures of MR trunction rtefcts. AJNR 9: Enzmnn DR (1990) Syringomyeli. In: Enzmnn DR, De L Pz RL, Ruin JB (eds) Mgnetic resonnce of the spine. Mosy, St Louis 8. Enzmnn DR (1991) Imging of syringomyeli. In: Btzdorf U (ed) Syringomyeli. Willims nd Wilkins, Bltimore 9. Enzmnn DR, Pelc M (1991) Norml flow ptterns of intrcrnil nd spinl cerehrospinl fluid defined with phse-contrst cine MR imging. Rdiology 178: Levy LM, DI Chiro G (1990) MR phse imging nd cererospinl fluid flow in the hed nd spine. Neurordiology 5: Quencer RM, Donovn Post MJ, Hinks RJ, et l (1990) Cine MR in the evlution of norml nd norml CSF flow: intrcrnil nd intrspinl studies. Neurordiology 5: Wilims B (1991) Pthogenesis of syringomyeli. In: Btzdorf U (ed) Syringomyeli. Willims nd Wilkins, Bltimore Correspondence: H. L. J. Tnghe, M.D., Deprtment of Rdiodignostics, University Hospitl Dijkzigt, Dr. Molewterplein 40, 3015 GD Rotterdm, The Netherlnds.