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ISBN X7-16-15078-3 ISSN 0065-1437

Utility of ictal SPECT: peri-ictal, post-ictal Weis M, Feistel H. Stefan H. Utility of ictal SPECT: peri-ictal. post-ictal. Acta Neurol Scand 1994: Suppl. 152: 145-147

In addition to the statements of Ma'rkand and Wieser we want to present the results with interictal and peri-ictal HMPAO-SPECTs at the Epilepsy Center in Erlangen.

Methods

40 patients with refractory unilateral temporal lobe epilepsy (TLE) were examined by ictal and interic- tal SPECT. In 12 patients interictal, ictal and post- ictal SPECT studies were performed. Interictal SPECT was performed EEG controlled in a seiz- ure-free period. Peri-ictal SPECT, ictal and early postictal SPECT, were obtained during the presur- gical evaluation. For ictal SPECT 99mTc-HMPAO was injected during the seizures with a mean injec- tion latency of 61 sec (range: 32-97 s) after seizure onset. The postictal SPECT were obtained by injec- tion of 99mTc-HMPAO 2 to 7 min after the end of the seizures. Mean injection latency for postictal SPECT was 3 min after the end of the seizure. 99mTc-HMPAO was used as tracer for interictal, ictal and postictal SPECT. Scans were obtained using a ROTA-ZLC37 double head rotating scintil- lation camera (Siemens, Germany) and analysed visually and semiquantitatively according to the methods described previously (1).

Results

In all, 67% of the patients had patterns of focal hypoperfusion in interictal SPECT. In 27.5% of the patients interictal SPECT were without patholog- ical results (Table 1). Only in one patient localis- ation by interictal SPECT was wrong in form of incorrect frontal hypoperfusion.

Ictal SPECT showed pathological results in the form of focal hyperperfusion in 75% of the pa-

M. Weis', H. Feistel', H. Stefan' Department of 'Neurology, 'Nuclearmedicine, University of Erlangen-Nurnberg, Germany

Key words: SPECT; ictal.

tients. In 12.5% of the patients focal hypoperfusion was observed and in 7.5% of the patients ictal SPECTS were without pathological findings (Table 1). Wrong localisations were obtained in 2 patients, one patient with focal frontal hyperperfusion, one patient with bitemporal hyperperfusion. In 23% of the patients only ictal SPECT confirmed the EEG focus. Lateralisation and regionalisation in ictal and in interictal SPECT were correct in all 30 patients with outcome ENGEL 1/11 after surgery.

The results of ictal SPECT were analysed in relation to their injection latency and in relation to results of cranial MRI in these patients. The mean injection latencies for SPECTs with focal hyperperfusion were 51 s in contrast to an injection latency of 72 s for SPECT without focal hyperper- fusion or with wrong results (Fig. 1).

MRI was performed in all patients (no patholog- ical findings - 11 patients; atrophy or focal sclerosis - 16 patients; tumors - 5 patients; substancy defects - 3 patients; angioma ~ 2 patients; cysts - 2 pa- tients; cavernoma - l patient). Focal hyperper- fusion in ictal SPECT was obtained in 88% of the patients without pathological findings in MRI and in 92% of the patients with focal atrophy or mesial sclcrosis in MRI, but only in 56% in the patients group with tumors, agiomas and other patholog- ical findings in MRI (Fig. 2). In 33% of these

Table 1. lctal and interictal SPECT (40 patients with unilateral TLE)

focal focal no wrong hyperperfusion hypoperfusion localisation localisation

ictal 30 5 3 2 SPECT (75%) (1 2.5%) (7.5%) (5%) interictal 1 27 11 1 SPECT (2 5%) (67,5%) (27.5%) (2.5%)

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Weis et al.

I

I I

Q P

food m a w resllt

Fig. 1. Shorter injection latency in ictal SPECTs with focal hyperperfusion

patients there were hypoperfused foci in ictal SPECT. In this group there were good results in interictal SPECT. There was in 78% focal hypoper- fucion in interictal SPECTs.

First results of a correlation analysis of interic- tal, ictal and postictal SPECT in the same patients (n = 12; unilateral TLE) show focal changes of cer- ebral perfusion in the region of the EEG focus in 75”/0 of the postictal SPECT, in 91% of the ictal SPECT and in 60% of the interictal SPECT. In

MRI:

no pathological result

atrophylscleroris

tumorlangiomalsubstanc

Fig. 2. Ictal SPECT (30 patients with unilateral TLE - outcome ENGEL 1/11 after surgery)

difference to the interictal SPECT in these patients localisation by postictal SPECT was better in pa- tients without pathological findings in MRI (Fig. 3). But there still remain 10% of patients where only the ictal SPECT confirmed the EEG focus.

Discussion

The presented results show that ictal 99mTc- HMPAO-SPECTs provide a high amount of infor- mation in TLE (Table 1). Their sensitivity was similar to 123J-HIDPM studies (2). But HMPAO has the advantages of lower costs, wide availability

0

%

pathological MRI pottictal SPECT

ictal SPECT SPECT

Fig. 3. Correct localisation in interictal, ictal and postictal SPECT (12 patients with unilateral TLE)

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Utility of SPECT

ings. Best information will be obtained by com- bined interictal and peri-ictal SPECT studies.

combined with better imaging characteristics ( 3 ) . Independently of the tracers used by the different groups. the timing of their application plays an important role for the results of ictal SPECT. The comparision of injection latencies of ictal SPECT with and without focal hyperperfusion shows that rapid injection improves the detection of focal re- gional hyperperfusion (Fig. 1). These findings are supported by peri-ictal studies which showed rapid changes in the pattern of cerebral blood flow distri- bution form the ictal to the postictal states (4). A correlation analysis of ictal and postictal SPECT in the same patients confirmed these results by better localisation with ictal than with early postic- tal studies (Fig. 3).

SPECT can be used as a confirmatory test and in especially high value in case of “negative” MRI (Fig. 2) or in case of ambiguous scalp EEG find-

References

I . STEFAY H, BAUER J. FEISTEI. H. et al. Regional cerebral blood flow during focal seizures of temporal and frontocen- tral onset. Ann Neurol 1990: 27: 162-166.

2. MARFAND OM. SALVONA V, WORTH RM, PARK HM, WELLMAN HM. Ictal brain imaging in presurgical evalu- ation of patients with medically intractable complex partial seizures. Acta Neurol Scand 1994: Suppl 157: 137-144.

3. LEONARD JP. NOWOTNIK DP. NEIRINCKX RD. Technitiuni- 99m-d. I-HM-PAO: a new radiopharmaceutical for imag- ing regional brain perfusion using SPECT: a comparison with Jodine-173 HIDPM. J Nucl Med 1989: 77: 1819-1823.

4. ROWE CC, BERKOVIC SF. AUSTIN MC, MCKAY WJ, BLAIXN PF. Patterns of postictal cerebral blood flow i n temporal lobe epilepsy: qualititive and quantitative analysis. Neurol- ogy 1991: 41: 1096-1 103.

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