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Dysembryoplastic neuroepithelial tumour as a potentially treatable cause of intractable epilepsy in children
ClinicalRadiology (1993) 47, 255-258
Dysembryoplastic Neuroepithelial Tumour as a Potentially Treatable Cause of Intractable Epilepsy in Children A. M . V A L I , M . A . C L A R K E *
a n d A. K E L S E Y t
Departments of Radiology, *Neurology and~fPathology, Booth Hall Children's Hospital, Manchester Dysembryoplastic neuroepithelial tumour (DNT) represents a morphologically unique and surgically treatable benign lesion typically associated with complex partial seizures (CPS). Although the radiological features are not pathognomonic the histology is quite distinct. They may account for a significant minority of children with intractable CPS. We present four histologically proven cases to demonstrate and discuss the range of radiological features. Recent recognition that CPS may be caused by a number of conditions including DNT emphasizes that all children with partial seizures should have radiological investigations early in their course. Vali, A . M . , C l a r k e , M . A . & K e t s e y , A . (1993). Clinical Radiology 47, 2 5 5 - 2 5 8 . D y s e m b r y o p l a s t i c N e u r o e p i t h e l i a l T u m o u r as a Potentially T r e a t a b l e C a u s e o f I n t r a c t a b l e 9E p i l e p s y i n C h i l d r e n
Accepted for Publication 2 November 1992
A recent study of an unselected population of children with partial seizures but no neurological signs d e m o n strated that 5% have structural lesions demonstrable on computed tomography (CT) of potential therapeutic significance [1]. Dysembryoplastic neuroepithelial t u m o u r ( D N T ) h a s r e c e n t l y b e e n r e c o g n i z e d as a c a u s e o f c o m p l e x p a r t i a l s e i z u r e s ( C P S ) [2]. T h i s e m p h a s i z e s t h a t all c h i l d r e n w i t h p a r t i a l s e i z u r e s s h o u l d b e i n v e s t i g a t e d e a r l y in t h e i r c o u r s e . A s e a r c h o f t h e B r i t i s h r a d i o l o g i c a l literature reveals no reports of DNT. We report four histologically p r o v e n cases.
CASE REPORTS
Case 1. This boy presented with tonic seizures at 6 months of age. Initial treatment with Clonazepam resulted in reduction in seizures which had been occurring in clusters once or twice a day. Birth was normal but there was mild generalized developmental delay. There were no abnormalities on neui'ological examination. Electroencephalogram (EEG) was abnormal and showed frequent generalized sharp slow complexes. Between the discharges there was attenuation of electrocerebral activity. Cranial CT (Fig. 1) at 14 months of age showed a rounded focal area of reduced attenuation in the right temporal lobe. It showed no enhancement with contrast. The lesion measured about 2 cm in diameter and demonstrated no significant mass effect. A right temporal craniotomy and lobectomy were carried out but the tumour removal was not thought to be complete. At 389 years the child was seizure-free a n d on no anticonvulsants. Development and EEG were normal. Cranial CT showed no evidence of tumour recurrence. Case 2. This 389 girl presented with a 289 year history of complex partial seizures and behavioural difficulties. Episodes of eye watering, chewing and impaired awareness had been noted from the age of 10 months. At 18 months, seizures became very severe, one arm or the other would elevate, awareness was impaired and progression to a generalized tonic clonic seizure frequent. Sodium valproate was prescribed with good effect until the age of 3 when there was a deterioration in her epilepsy with a serial. Increase in Valproate failed to control the seizures. Standard EEG recording showed generalized abnormalities with sharp activity most marked in the vertex. Sleep recording showed frequent sharp low activity phase reversing in, the left temporal region. The obstetric history was unremarkable and there was no family history of epilepsy. No neurological signs were present between seizures. Correspondence to: A. M. Vali, Department of Radiology, Booth Hall Children's Hospital, Manchester M9 2AA.
Fig. 1 Contrast CT showing a rounded non-enhancing area of reduced attenuation in the right temporal lobe (image inverted left to right).
CT scan (Fig. 2) showed a densely calcified nodule in the left parasellar region in the medial aspect of the temporal lobe. Part of the lesion was solid and part of it was low attenuation with calcification in its wall. The lower attenuation component was equivalent to CSF density. No convincing contrast enhancement was seen. The appearances were those of a low grade cystic tumour. At surgery a small cyst associated with pinkish grey tumour was found in the medial part of the left temporal lobe with extension beneath the internal carotid artery. The temporal lobe component was resected. She made an excellent post-operative recovery. She was maintained on sodium valproate 800 mg daily and was free of fits. Ten months later sodium valproate was stopped but she had three fits and it was recommenced. Follow-up scan 1 year later showed no evidence of recurrence. Behavioural difficulties have persisted. Case 3. This previously well 9-year-old boy presented with a 3 month history of episodes of impaired awareness associated with fumbling movements of his hands. There was no lateralized motor features, no neurological signs and EEG showed a spike and slow wave activity in
256
CLINICAL RADIOLOGY
Fig. 4 - Contrast CT showing a well defined non-enhancing low density (4HU) lesion in the right temporal lobe (image inverted left to right).
Fig. 2 - Unenhanced CT showing a partially calcified low density lesion in the left parasellar region (image inverted left to right).
signal on Tl-weighted images. There was generalized temporal lobe enlargement. Full right temporal lobectomy was carried out at operation. He made an uneventful post-operative recovery and was discharged home on Carbamazepine 100 mg tds, and has not had any further seizures. Case 4. This 12-year-old girl presented with a 3 year history of complex partial seizures occurring in clusters of 3 to 4 seizures every 2 weeks. The seizures were preceded by a feeling of fear that someone or something.was behind her. Following this, aura awareness was impaired for 2-3 min and though able to talk, verbal responses were inappropriate. There were no lateralized motor features. Neurological examination was normal and EEG showed poorly localized slow activity posteriorly. Cranial CT revealed a well defined non-enhancing low density lesion (4 Hounsfield units) in the middle and posterior right temporal lobe (Fig. 4). There was anterior displacement of the middle cerebral artery but no ventricular dilatation was seen. A polar temporal lobectomy was carried out. The tumour was encountered posteriorly and medially extending backwards along the medial aspect of the temporal horn almost to the trigone. Complete removal of the tumour could not be achieved. Post-operatively the seizures have persisted but at a much reduced frequency.
DISCUSSION
Fig. 3 Coronal T2-weighted image (TR 2000, TE 90) showing increased signal in the right temporal lobe. the right fronto-temporal regions. A diagnosis of complex partial epilepsy was made. Cranial CT scan revealed a right temporal low attenuation area with suggestion of some peripheral enhancement and mass effect. Magnetic resonance imaging (MRI) showed generalized increased signal on T2weighted images confined to the right temporal lobe (Fig. 3) and was low
The four tumours showed similar histology which was in k e e p i n g w i t h d y s e m b r y o p l a s t i c n e u r o e p i t h e l i a l t u m o u r ( F i g s 5 a n d 6). T h e y all h a d a m u l t i n o d u l a r a r c h i t e c t u r e a n d w e r e s i t u a t e d m a i n l y in the c o r t e x b u t e x t e n d e d i n t o the w h i t e m a t t e r . T h e t u m o u r s w e r e c o m p o s e d o f o l i g o d e n d r o c y t e s , a s t r o c y t e s a n d n e u r o n s , t h e l a t t e r b e i n g seen p r e d o m i n a n t l y in p o o l s o f m u c i n o u s m a t r i x . T h e r e w a s also e v i d e n c e o f m i l d c o r t i c a l d y s p l a s i a w i t h l a c k o f l a m i n a t i o n . T w o o f the t u m o u r s s h o w e d foci o f calcification. T h e t r u e i n c i d e n c e o f this lesion is as yet u n k n o w n as this e n t i t y has o n l y b e e n r e c e n t l y r e c o g n i z e d [2]. P r o s p e c tive a n d r e t r o s p e c t i v e studies o f t u m o u r s o c c u r r i n g in c h i l d r e n w i t h C P S will h o p e f u l l y p r o v i d e i n f o r m a t i o n to e l u c i d a t e n o t o n l y the i n c i d e n c e b u t also the b i o l o g i c a l
DYSEMBRYOPLASTIC NEUROEPITHELIAL TUMOUR IN EPILEPSY
Fig. 5 - P h o t o m i c r o g r a p h showing nodular nature of the tumour involving cortex and white matter (Haematoxylin-eosin stain) ( • 40).
Fig. 6 - Haematoxylin-eosin stained section showing mixed oligoastrocytoma ( x 246).
behaviour of these tumours. To date it appears that this tumour does not recur even in cases where removal was considered incomplete [2]. In three o f our cases, tumours were incompletely excised. Two of these children have had repeat cranial CT at 1 and 2 years post-surgery respectively, and there is no evidence of recurrence. It is therefore Felt that there is unlikely to be a place for radiotherapy. The results for seizure control were good, as 70% or more of patients with these tumours, or with other benign
257
tumours, achieve complete freedom from seizures by resective surgery [3-5]. CT in our cases showed a fairly well demarcated low attenuation lesion in the temporal lobe. In none of the cases was the pattern of hypodensity suggestive of peritumoural oedema. Associated focal contrast enhancement (18%) and calcification (23 %) has been reported [2]. It is suggested that the peripheral contrast enhancement in one of our cases is possibly caused by very frequent seizures resulting in the breakdown of the blood brain barrier due to ischaemia. The precise mechanism however, is unknown. In the previously reported series five out of 35 patients who had angiography demonstrated 'shift' of the normal structures. Subtle mass effects are better demonstrated with modern imaging (CT and MRI) where grey matter/white matter interface and temporal horns are seen (Fig. 3). Thin (5 mm) temporal lobe orientated CT sections can limit the extent of bone artifact and provide more slices of the anterior part of the temporal lobe. CT differential diagnosis of D N T includes arachnoid cysts as well as low grade gliomas and other forms of hamartomata. Arachnoid cysts can be distinguished by their extra-axial location and homogenous cerebrospinal fluid density. The intra-axial lesions may prove difficult to differentiate but a peripherally placed, well demarcated, low density lesion involving the cortex should raise a suspicion of DNT. One patient had MRI which displayed prolonged TI and T2 relaxation times and subtle space occupation suggesting the diagnosis of a low grade neoplasm. Several studies indicate that such lesions may be shown by MRI when they are unrecognized or invisible by CT scanning [6,7]. MRI is not degraded by bone artifact, nor limited to axial or paraxial scan planes, and different scan sequences will provide either maximal spatial or contrast information [3]. Single photon emission tomography (SPECT) has also been used to help lateralize the epileptic focus. The principle that 'focal seizures suggest focal pathology' has been illustrated in several studies [7-9]. EEG findings are not characteristic. In young children with CPS the EEG abnormality with standard skull electrodes often shows generalized and not localized abnormalities. Sleep electrodes may allow demonstration o f focal EEG abnormalities when standard electrodes show generalized changes. Radiological signs suggesting the lesion is of long standing include deformity of the overlying calvarium, enlargement of the temporal fossa, calcification visible on skull X-ray and angiographic signs o f hypoplastic vascularization. All reported cases have been supratentorial and have involved the temporal lobe in 62%, frontal lobe in 31% and parietal and occipital lobes in a small minority, while deeply situated or midline tumours have not been reported [2]. It is hoped that with growing experience D N T will be reliably identified by modern non-'invasive neuroimaging techniques of CT, MRI and SPECT, thus reducing the necessity of angiography in these patients. The failure to detect these lesions in the pre-CT era, coupled with the reluctance to consider surgery in the medically refractory partial seizures, may well have allowed these tumours to go unrecognized as a clinico-pathological entity. Awareness of the existence of DNT, the early age of clinical presentation and characteristic CT appearance of a cystlike hypodense cortical component permit pre-operative suspicion of the diagnosis, and a reduction in morbidity
258
CLINICAL RADIOLOGY
due to early detection. Unnecessary radio and/or chemotherapy following surgery in these young patients can also be avoided.
Acknowledgements. We wish to thank Mr Richard Cowie for the permission to report these cases, Dr Ian Turnbull and Dr Jennifer Weller for their helpful advice, Dr Charles Hutchinson (University Department) for providing the MRI and Mrs Jean Bowles and Mrs Sandra Fowley for typing the manuscript.
REFERENCES 1 Minford AMB, Forsythe WI. Computed tomography findings in partial seizures. Archives of Disease in Childhood 1992;67:693-696. 2 Daumas-Duport C, Schoithauer BW, Chodkiewicz JP, Laws E, Vendrenne C. Dysembryoplastic neuroepithelial tumour: surgically
curable tumour of young patients with intractable partial seizure. Neurosurgery 1988;23:545-556. 3 Adams CBT, Anslow OWP, Molyneaux A, Oxbury J. Radiological detection of surgically treatable lesions In: Engel J, ed. Surgical treatment of epilepsies. New York: Raven, 1987:213-233. 4 Cahan LD, Engel J. Surgery for epilepsy: a review. Acta Neurologica Scandinavica 1986;73:551-560. 5 0 l i v i e r A. Risk and benefit in the surgery of epilepsy: complications and positive results on seizure tendency and intellectual function. Acta Neurologica Scandinavica (Suppl.) 1988;117:114 121. 6 Sperling MR, Wilson G, Engel J, Babb TL, Phelps M, Bradley W. Magnetic resonance imaging in intractable partial epilepsy: correlative studies. Annals of Neurology 1986;20:57-62. 7 Duncan R, Patterson J, Hadley DM, Macpherson P, Brodie M J, Bone I e t al. CT, MR and SPECT imaging in temporal lobe epilepsy. Journal of Neurology, Neurosurgery and Psychiatry 1990;53:11-15. 8 Gastaut H, Gastaut HL. Computerized transverse axial tomography in epilepsy. Epilepsia 1976;17:325-336. 9 Yang PJ, Berger PE, Cohen ME, Duffner PK. Computed tomography and childhood seizure disorders. Neurology 1979;29:1084-1088.
Dysembryoplastic Neuroepithelial Tumour as a Potentially Treatable Cause of Intractable Epilepsy in Children A. M . V A L I , M . A . C L A R K E *
a n d A. K E L S E Y t
Departments of Radiology, *Neurology and~fPathology, Booth Hall Children's Hospital, Manchester Dysembryoplastic neuroepithelial tumour (DNT) represents a morphologically unique and surgically treatable benign lesion typically associated with complex partial seizures (CPS). Although the radiological features are not pathognomonic the histology is quite distinct. They may account for a significant minority of children with intractable CPS. We present four histologically proven cases to demonstrate and discuss the range of radiological features. Recent recognition that CPS may be caused by a number of conditions including DNT emphasizes that all children with partial seizures should have radiological investigations early in their course. Vali, A . M . , C l a r k e , M . A . & K e t s e y , A . (1993). Clinical Radiology 47, 2 5 5 - 2 5 8 . D y s e m b r y o p l a s t i c N e u r o e p i t h e l i a l T u m o u r as a Potentially T r e a t a b l e C a u s e o f I n t r a c t a b l e 9E p i l e p s y i n C h i l d r e n
Accepted for Publication 2 November 1992
A recent study of an unselected population of children with partial seizures but no neurological signs d e m o n strated that 5% have structural lesions demonstrable on computed tomography (CT) of potential therapeutic significance [1]. Dysembryoplastic neuroepithelial t u m o u r ( D N T ) h a s r e c e n t l y b e e n r e c o g n i z e d as a c a u s e o f c o m p l e x p a r t i a l s e i z u r e s ( C P S ) [2]. T h i s e m p h a s i z e s t h a t all c h i l d r e n w i t h p a r t i a l s e i z u r e s s h o u l d b e i n v e s t i g a t e d e a r l y in t h e i r c o u r s e . A s e a r c h o f t h e B r i t i s h r a d i o l o g i c a l literature reveals no reports of DNT. We report four histologically p r o v e n cases.
CASE REPORTS
Case 1. This boy presented with tonic seizures at 6 months of age. Initial treatment with Clonazepam resulted in reduction in seizures which had been occurring in clusters once or twice a day. Birth was normal but there was mild generalized developmental delay. There were no abnormalities on neui'ological examination. Electroencephalogram (EEG) was abnormal and showed frequent generalized sharp slow complexes. Between the discharges there was attenuation of electrocerebral activity. Cranial CT (Fig. 1) at 14 months of age showed a rounded focal area of reduced attenuation in the right temporal lobe. It showed no enhancement with contrast. The lesion measured about 2 cm in diameter and demonstrated no significant mass effect. A right temporal craniotomy and lobectomy were carried out but the tumour removal was not thought to be complete. At 389 years the child was seizure-free a n d on no anticonvulsants. Development and EEG were normal. Cranial CT showed no evidence of tumour recurrence. Case 2. This 389 girl presented with a 289 year history of complex partial seizures and behavioural difficulties. Episodes of eye watering, chewing and impaired awareness had been noted from the age of 10 months. At 18 months, seizures became very severe, one arm or the other would elevate, awareness was impaired and progression to a generalized tonic clonic seizure frequent. Sodium valproate was prescribed with good effect until the age of 3 when there was a deterioration in her epilepsy with a serial. Increase in Valproate failed to control the seizures. Standard EEG recording showed generalized abnormalities with sharp activity most marked in the vertex. Sleep recording showed frequent sharp low activity phase reversing in, the left temporal region. The obstetric history was unremarkable and there was no family history of epilepsy. No neurological signs were present between seizures. Correspondence to: A. M. Vali, Department of Radiology, Booth Hall Children's Hospital, Manchester M9 2AA.
Fig. 1 Contrast CT showing a rounded non-enhancing area of reduced attenuation in the right temporal lobe (image inverted left to right).
CT scan (Fig. 2) showed a densely calcified nodule in the left parasellar region in the medial aspect of the temporal lobe. Part of the lesion was solid and part of it was low attenuation with calcification in its wall. The lower attenuation component was equivalent to CSF density. No convincing contrast enhancement was seen. The appearances were those of a low grade cystic tumour. At surgery a small cyst associated with pinkish grey tumour was found in the medial part of the left temporal lobe with extension beneath the internal carotid artery. The temporal lobe component was resected. She made an excellent post-operative recovery. She was maintained on sodium valproate 800 mg daily and was free of fits. Ten months later sodium valproate was stopped but she had three fits and it was recommenced. Follow-up scan 1 year later showed no evidence of recurrence. Behavioural difficulties have persisted. Case 3. This previously well 9-year-old boy presented with a 3 month history of episodes of impaired awareness associated with fumbling movements of his hands. There was no lateralized motor features, no neurological signs and EEG showed a spike and slow wave activity in
256
CLINICAL RADIOLOGY
Fig. 4 - Contrast CT showing a well defined non-enhancing low density (4HU) lesion in the right temporal lobe (image inverted left to right).
Fig. 2 - Unenhanced CT showing a partially calcified low density lesion in the left parasellar region (image inverted left to right).
signal on Tl-weighted images. There was generalized temporal lobe enlargement. Full right temporal lobectomy was carried out at operation. He made an uneventful post-operative recovery and was discharged home on Carbamazepine 100 mg tds, and has not had any further seizures. Case 4. This 12-year-old girl presented with a 3 year history of complex partial seizures occurring in clusters of 3 to 4 seizures every 2 weeks. The seizures were preceded by a feeling of fear that someone or something.was behind her. Following this, aura awareness was impaired for 2-3 min and though able to talk, verbal responses were inappropriate. There were no lateralized motor features. Neurological examination was normal and EEG showed poorly localized slow activity posteriorly. Cranial CT revealed a well defined non-enhancing low density lesion (4 Hounsfield units) in the middle and posterior right temporal lobe (Fig. 4). There was anterior displacement of the middle cerebral artery but no ventricular dilatation was seen. A polar temporal lobectomy was carried out. The tumour was encountered posteriorly and medially extending backwards along the medial aspect of the temporal horn almost to the trigone. Complete removal of the tumour could not be achieved. Post-operatively the seizures have persisted but at a much reduced frequency.
DISCUSSION
Fig. 3 Coronal T2-weighted image (TR 2000, TE 90) showing increased signal in the right temporal lobe. the right fronto-temporal regions. A diagnosis of complex partial epilepsy was made. Cranial CT scan revealed a right temporal low attenuation area with suggestion of some peripheral enhancement and mass effect. Magnetic resonance imaging (MRI) showed generalized increased signal on T2weighted images confined to the right temporal lobe (Fig. 3) and was low
The four tumours showed similar histology which was in k e e p i n g w i t h d y s e m b r y o p l a s t i c n e u r o e p i t h e l i a l t u m o u r ( F i g s 5 a n d 6). T h e y all h a d a m u l t i n o d u l a r a r c h i t e c t u r e a n d w e r e s i t u a t e d m a i n l y in the c o r t e x b u t e x t e n d e d i n t o the w h i t e m a t t e r . T h e t u m o u r s w e r e c o m p o s e d o f o l i g o d e n d r o c y t e s , a s t r o c y t e s a n d n e u r o n s , t h e l a t t e r b e i n g seen p r e d o m i n a n t l y in p o o l s o f m u c i n o u s m a t r i x . T h e r e w a s also e v i d e n c e o f m i l d c o r t i c a l d y s p l a s i a w i t h l a c k o f l a m i n a t i o n . T w o o f the t u m o u r s s h o w e d foci o f calcification. T h e t r u e i n c i d e n c e o f this lesion is as yet u n k n o w n as this e n t i t y has o n l y b e e n r e c e n t l y r e c o g n i z e d [2]. P r o s p e c tive a n d r e t r o s p e c t i v e studies o f t u m o u r s o c c u r r i n g in c h i l d r e n w i t h C P S will h o p e f u l l y p r o v i d e i n f o r m a t i o n to e l u c i d a t e n o t o n l y the i n c i d e n c e b u t also the b i o l o g i c a l
DYSEMBRYOPLASTIC NEUROEPITHELIAL TUMOUR IN EPILEPSY
Fig. 5 - P h o t o m i c r o g r a p h showing nodular nature of the tumour involving cortex and white matter (Haematoxylin-eosin stain) ( • 40).
Fig. 6 - Haematoxylin-eosin stained section showing mixed oligoastrocytoma ( x 246).
behaviour of these tumours. To date it appears that this tumour does not recur even in cases where removal was considered incomplete [2]. In three o f our cases, tumours were incompletely excised. Two of these children have had repeat cranial CT at 1 and 2 years post-surgery respectively, and there is no evidence of recurrence. It is therefore Felt that there is unlikely to be a place for radiotherapy. The results for seizure control were good, as 70% or more of patients with these tumours, or with other benign
257
tumours, achieve complete freedom from seizures by resective surgery [3-5]. CT in our cases showed a fairly well demarcated low attenuation lesion in the temporal lobe. In none of the cases was the pattern of hypodensity suggestive of peritumoural oedema. Associated focal contrast enhancement (18%) and calcification (23 %) has been reported [2]. It is suggested that the peripheral contrast enhancement in one of our cases is possibly caused by very frequent seizures resulting in the breakdown of the blood brain barrier due to ischaemia. The precise mechanism however, is unknown. In the previously reported series five out of 35 patients who had angiography demonstrated 'shift' of the normal structures. Subtle mass effects are better demonstrated with modern imaging (CT and MRI) where grey matter/white matter interface and temporal horns are seen (Fig. 3). Thin (5 mm) temporal lobe orientated CT sections can limit the extent of bone artifact and provide more slices of the anterior part of the temporal lobe. CT differential diagnosis of D N T includes arachnoid cysts as well as low grade gliomas and other forms of hamartomata. Arachnoid cysts can be distinguished by their extra-axial location and homogenous cerebrospinal fluid density. The intra-axial lesions may prove difficult to differentiate but a peripherally placed, well demarcated, low density lesion involving the cortex should raise a suspicion of DNT. One patient had MRI which displayed prolonged TI and T2 relaxation times and subtle space occupation suggesting the diagnosis of a low grade neoplasm. Several studies indicate that such lesions may be shown by MRI when they are unrecognized or invisible by CT scanning [6,7]. MRI is not degraded by bone artifact, nor limited to axial or paraxial scan planes, and different scan sequences will provide either maximal spatial or contrast information [3]. Single photon emission tomography (SPECT) has also been used to help lateralize the epileptic focus. The principle that 'focal seizures suggest focal pathology' has been illustrated in several studies [7-9]. EEG findings are not characteristic. In young children with CPS the EEG abnormality with standard skull electrodes often shows generalized and not localized abnormalities. Sleep electrodes may allow demonstration o f focal EEG abnormalities when standard electrodes show generalized changes. Radiological signs suggesting the lesion is of long standing include deformity of the overlying calvarium, enlargement of the temporal fossa, calcification visible on skull X-ray and angiographic signs o f hypoplastic vascularization. All reported cases have been supratentorial and have involved the temporal lobe in 62%, frontal lobe in 31% and parietal and occipital lobes in a small minority, while deeply situated or midline tumours have not been reported [2]. It is hoped that with growing experience D N T will be reliably identified by modern non-'invasive neuroimaging techniques of CT, MRI and SPECT, thus reducing the necessity of angiography in these patients. The failure to detect these lesions in the pre-CT era, coupled with the reluctance to consider surgery in the medically refractory partial seizures, may well have allowed these tumours to go unrecognized as a clinico-pathological entity. Awareness of the existence of DNT, the early age of clinical presentation and characteristic CT appearance of a cystlike hypodense cortical component permit pre-operative suspicion of the diagnosis, and a reduction in morbidity
258
CLINICAL RADIOLOGY
due to early detection. Unnecessary radio and/or chemotherapy following surgery in these young patients can also be avoided.
Acknowledgements. We wish to thank Mr Richard Cowie for the permission to report these cases, Dr Ian Turnbull and Dr Jennifer Weller for their helpful advice, Dr Charles Hutchinson (University Department) for providing the MRI and Mrs Jean Bowles and Mrs Sandra Fowley for typing the manuscript.
REFERENCES 1 Minford AMB, Forsythe WI. Computed tomography findings in partial seizures. Archives of Disease in Childhood 1992;67:693-696. 2 Daumas-Duport C, Schoithauer BW, Chodkiewicz JP, Laws E, Vendrenne C. Dysembryoplastic neuroepithelial tumour: surgically
curable tumour of young patients with intractable partial seizure. Neurosurgery 1988;23:545-556. 3 Adams CBT, Anslow OWP, Molyneaux A, Oxbury J. Radiological detection of surgically treatable lesions In: Engel J, ed. Surgical treatment of epilepsies. New York: Raven, 1987:213-233. 4 Cahan LD, Engel J. Surgery for epilepsy: a review. Acta Neurologica Scandinavica 1986;73:551-560. 5 0 l i v i e r A. Risk and benefit in the surgery of epilepsy: complications and positive results on seizure tendency and intellectual function. Acta Neurologica Scandinavica (Suppl.) 1988;117:114 121. 6 Sperling MR, Wilson G, Engel J, Babb TL, Phelps M, Bradley W. Magnetic resonance imaging in intractable partial epilepsy: correlative studies. Annals of Neurology 1986;20:57-62. 7 Duncan R, Patterson J, Hadley DM, Macpherson P, Brodie M J, Bone I e t al. CT, MR and SPECT imaging in temporal lobe epilepsy. Journal of Neurology, Neurosurgery and Psychiatry 1990;53:11-15. 8 Gastaut H, Gastaut HL. Computerized transverse axial tomography in epilepsy. Epilepsia 1976;17:325-336. 9 Yang PJ, Berger PE, Cohen ME, Duffner PK. Computed tomography and childhood seizure disorders. Neurology 1979;29:1084-1088.