Sonographic Recognition of Unilateral Megalencephaly P. Babyn, MDCM, S. Chuang, MD, A. Daneman, MD, C. Withers, MD
With the increasing use of sonography both for prenatal screening and for initial intracranial evaluation in the neonatal period, earlier diagnosis of many congen• ital anomalies is now possible, allowing for better counseling and parent preparation. Unilateral megalencephaly is a rare cerebral congenital malformation of unknown origin with features of a localized migra· tion anomaly of variable severity. We report the realtime sonographic findings in two cases. A characteristic if not diagnostic ultrasonic appearance, not previously described, is presented that can be seen both in utero and postnatally.
CASE REPORT CASE 1 This case was reported in detail previousJyb; however, the sonographic features were not described. A 2,500 g male infant was born to a 23 year old gravida 3, para 1 mother at 36 weeks of gestation. The pregnancy was complicated by gestational diabetes controlled by diet only. Prenatal sonograms (not available) obtained at an outside institution reported marked progressive increase in biparietal diameter-abdominal circumference ratio at 3 to 4 months of gestation and 1 week prior to delivery. No com· ment was made on the intracranial appearance. There was spontaneous rupture of the membrane with green liquor passed. Oxytocin (Syntocinon) administration was commenced and vacuum extraction performed because of late Received November 25, 1991, from the Department of Diagnostic Imaging (P.B., S.C., A.D.), Hospital for Sick Childre n, Toronto, Ontario, and Department of Radiology (C.W.), SunnyBrook Hospital, North York, Ontario. Revised manuscript accepted for publication May 29, 1992. Address correspondence and reprint requests to Paul Babyn, MD, Department of Diagnostic Imaging, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada, MSG 1X8.
decelerations. Apgar scores were 5 at 1 minute, 6 at 5 minutes, and 7 at 10 minutes. Physical examination showed a large cranial vault with bulging fontanelles, prominent occiput, low+set ears, and wide sutures. The head circumference was 38 em. A pulsatile mass was palpable on the left side of the cranium with an audible bruit.. The chest was hyperdynamic with a loud 51 · 52 grade 4/ 6 systolic murmur. The liver was enlarged. The child was hypotonic. All reflexes were symmetric at 1+. Echocardiography demonstrated shift of the heart to the right, cardiomegaly, and increased pulmonary vascularity. Chest radiograph also showed cardiomegaly with questionable congestive failure. Laboratory examination was remarkable for persistent hypoglycemia. Cranial ultrasonography showed asymmetry of the hemispheres with an enlarged left hemisphere and displacement of the superior sagittal fissure to the right (Fig. 1). The left lateral ventricle was enlarged and irregular in outline. The left cerebral hemisphere showed an increase in echogenicity compared to the right. The sulcal pattern on the right ap· peared normal, whereas that on the left was markedly dimin~ ished to absent, suggestive of lissencephaly. The right lateral ventricle was not seen, presumably because it was com• pressed by the expanded left hemisphere. Several areas of increased echogenicity were seen around the left ventricle, possibly calcific in origin. Abnormal cerebral vessels were noted in the region of the straight sinus. Doppler examination showed increased diastolic flow, but no definite arteriovenous malformation was seen. CT scanning followed by cerebral arteriography was performed. CT confirmed the presence of an enlarged left hemisphere and left lateral ventricle with shift of the midline to the right. Abnormally decreased sulcation was seen on the left, with a deep sylvian fissure. A small intraventricular hemorrhage was seen in the left occipital hom. Marked asymmetry between the attenuation of the two hemispheres was seen, thought to be compatible with right-sided infarction. Several small foci of calcification were observed around the left frontal hom. Arteriography demonstrated large ca· rotid arteries, no arteriovenous malformation, and enlarged
© 1992 by the American Institute of Ultrasound in Medicine • J Ultrasound Med 11:563-566, 1992 • 0278-4297/92/ $3.50
564
UNILATERAL MEGALENCEPHALY
Figure 1 Coronal ultrasonogram shows enlarged left lateral ventricle. Note shift of midline, homogeneous parenchymal l!chogenicity of left hemisphere with decreased sulcation, and nonvisualization of right lateral ventricle with deep left syl~ vian fissure (arrow) . anomalous venous sinuses on the left, particularly with shift of the midline. There was increased perfusion of the left hemisphere with rapid shunting of blood into the deep venous system. The infant's hypoglycemia could not be controlled, and he died from hepatic and cardiac failure. An autopsy was per· formed. Enlargement of the left lateral hemisphere, left brainstem, and spinal cord were noted. Severe dysplasia of the cerebral cortex, basal ganglia, and thalami including hippocampus was found with hypoplasia of the corpus callosum. Sulcation was abnormal, with pachygyria. The left lateral ventricle was enlarged and had a small intraventricular hemorrhage. Focal calcifications were found within the periventrkular cortex. The vascular system findings corresponded to those seen at arteriography. Microscopic examination showed neuronal heterotopia and cytomega]y, as well as cortical disorganiza· lion, compatible with unilateral megalencephaly.
CASE2 The second case is an infant girl born at 39 weeks of gestation by cesarean section to a 28 year old gravida 3, para 1 mother. The pregnancy was uncomplicated. Prenatal ultrasonography had shown a large head and left hemisphere interpreted as porencephaly. At birth the head circumference was greater than the 97th percentile at 41 em. It was unusually shaped, with marked prominence on the left. Seizure activity was noted on the first day of life, with jerky eye movements. The seizures became generalized tonicAclonic with arching of the back and backward rolling of the eyes lasting for 5 to 10 seconds. Jnitial treatment with phenobarbital did not ade· quately controJ the seizure activity, so the patient was
J Ultrasound Med 11:563- 566, 1992
switched to Mocadon and ACTH. The patient had multiple admissions for seizure control and pneumonia, Progressive developmental delay was first noted at approximately 6 weeks of age, with poor head control. All deep tendon reflexes were 1+ with questionable upgoing toes. The patient reacted to pain in all limbs. There was mild hypotonia. The electroencephalogram (EEG) showed marked depression of background activity with moderate abnormal spikes seen. Radiologic investigations included cranial computed tomography (CT), sonography, and magnetic resonance (MR) imaging. All imaging modalities demonstrated left hemispheric enlargement with shift of the midline to the right, large ipsilateral lateral ventricle, and abnormal sulcation. Retrospective review of the prenatal sonograms also demonstrated the ventricular hypertrophy and abnormal sulca· tion with prominent sylvian fissure (Fig. 2A). Cranial sonog~ raphy showed periventricular focally increased echogenicity (Fig. 28) corresponding to the calcifications seen on CT. MR imaging exquisitely demonstrated the abnormal increased cortical thickness and poor gray versus white matter differ~ entiation (Fig. 2C).
DISCUSSION Unilateral megalencephaly, also known as hemimegalencephaly, shows variable severity from mild lobar enlargement to marked distortion of the entire cerebral and cerebellar hemispheres, ipsilateral brainstem, and, quite rarely, even spinal cord.'-' The clinical presenta tion typically is early onset of seizures (before 4 months of age), which are usually progressive and unilateral, intractable, and associated with developmental delay and abnormal head growth. The pathologic findings have been described previously and depend on the severity of the disorder, with the most extreme cases showing areas of lissencephaly, polymicrogyria, and a thickened cortex with poor separation of gray and white matter.• Microscopically there is generalized disorganization of all cortical layers with giant neurons and heterotopia.'-' Treatment with hemispherectomy has been recommended.' Radiographic findings have been reported previously from angiographic, CT, and MR imaging studies. 1 ~ 4 • 6 As in our cases, CT and MR imaging generally show marked enlargement of the entire involved hemisphere with contralateral shift of the midline structures and lateral ventricular enlargement ipsilaterally. Additional findings include decreased sulcation, diminished operculization, and cortical thickening or localized involvement of the occipitoparietal region.2. 3 Decreased density of the white matter also was noted in several patients on CT scans, whereas MR imaging shows poor gray and white matter differentiation. On angiography, straightening, stretching, and separation of vessels is seen related to the enlargement of the hemisphere. Vascular enlargement and increased 4
J Ultrasound Med 11:563- 566,
BABYN ET AL
1992
565
A
c
8
perfusion to the point of arteriovenous shunting are rare, with our case 1 and one other having had conges· tive heart failure. The only previous mention of cranial ultrasonog· raphy in this disorder described increased echogenicity of the involved hemisphere. 2 As the pathologic features of unilateral megalencephaly include lissencephaly, it is not surprising that the sonographic features bear some resemblance to those previously described for lissencephaly.5• 7 The abnormal sulcal pattern, secondary to failure of migration, persists after the third or fourth month. The widened subarachnoid space within the sylvian fissure and enlarged ventricle are easily seen on ultrasonography. The enlarged ventricle should not be confused with unilateral hydrocephalus or porencephaly. The asymmetry of cortical density on CT also is reflected in the change in echogenicity. Associated calcifications also can be detected. We believe the sonographic findings just described to be characteristic of unilateral megalencephaly, cor·
Figure 2 A, Prenatal ultrasonogram obtained at 34 weeks of gestation showing left hemispheric enlargement, ipsilateral ventricular enlargement, and prominent sylvian fissure (ar• row). B, Coronal ultrasonogram at the level of the frontal horn on the right shows left hemispheric enlargement with shift of the midline to the right and focal areas of increased echogenicity corre5ponding to calcifications on CT. The over· all echogenicity of the left hemisphere is Jess than that on the right. Note abnormal sulcal pattern along interhemi* spheric fissure (arrllw). C, Axial MR image showing similar features to the ultrasonograms, with thickened cortex, en$ Jarged left lateral ventricle, and poor differentiation of gray and white matter.
relating well with previous CT and MR reports. It is hoped this will allow earlier diagnosis, especially pre· natally, affording better counseling to the parents and treatment to the child, as hemispherectomy is best performed before 6 months of age. 1
REFERENCES 1. King M, Stephenson JB, Zievogel M, eta!: Hemimegalen·
cephaly- a case for hemispherectomy? Neuropediatrics 16:46, 1985
566
UNILATERAL MEGALENCEPHALY
2. Fitz CR, Harwood-Nash DC, Boldt OW: The radiographic features of unilateral hemimegalencephaly. Neuroradiology 15:145. 1978 3. Barkovich AJ, Chuang SH: Unilateral megalencephaly: Correlation of MR imaging and pathologic characteristics. AJNR 11:523, 1990 4. Kalifa G, Sellier N, Demange P, et al: Hemimegalence· phaly: MR imaging in five children. Radiology 165:29, 1987
J Ultrasound Med 11:563- 566, 1992
5. Raminez RE: Sonographic recognition of lissencephaly (agyria). AJNR 5:830, 1984 6. Walters BC, Burrows PE, Musewe N, et al: Unilateral megalencephaly associated with neonatal high output cardiac failure. Childs Nerv Syst 6:123, 1990
7. Cioffi V, Bossi MC, Ballarati E, et al: Lissencephaly in two brothers detected by US. A "pseudo-liver• pattern. Pediatr Radio! 21 :512, 1991
With the increasing use of sonography both for prenatal screening and for initial intracranial evaluation in the neonatal period, earlier diagnosis of many congen• ital anomalies is now possible, allowing for better counseling and parent preparation. Unilateral megalencephaly is a rare cerebral congenital malformation of unknown origin with features of a localized migra· tion anomaly of variable severity. We report the realtime sonographic findings in two cases. A characteristic if not diagnostic ultrasonic appearance, not previously described, is presented that can be seen both in utero and postnatally.
CASE REPORT CASE 1 This case was reported in detail previousJyb; however, the sonographic features were not described. A 2,500 g male infant was born to a 23 year old gravida 3, para 1 mother at 36 weeks of gestation. The pregnancy was complicated by gestational diabetes controlled by diet only. Prenatal sonograms (not available) obtained at an outside institution reported marked progressive increase in biparietal diameter-abdominal circumference ratio at 3 to 4 months of gestation and 1 week prior to delivery. No com· ment was made on the intracranial appearance. There was spontaneous rupture of the membrane with green liquor passed. Oxytocin (Syntocinon) administration was commenced and vacuum extraction performed because of late Received November 25, 1991, from the Department of Diagnostic Imaging (P.B., S.C., A.D.), Hospital for Sick Childre n, Toronto, Ontario, and Department of Radiology (C.W.), SunnyBrook Hospital, North York, Ontario. Revised manuscript accepted for publication May 29, 1992. Address correspondence and reprint requests to Paul Babyn, MD, Department of Diagnostic Imaging, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada, MSG 1X8.
decelerations. Apgar scores were 5 at 1 minute, 6 at 5 minutes, and 7 at 10 minutes. Physical examination showed a large cranial vault with bulging fontanelles, prominent occiput, low+set ears, and wide sutures. The head circumference was 38 em. A pulsatile mass was palpable on the left side of the cranium with an audible bruit.. The chest was hyperdynamic with a loud 51 · 52 grade 4/ 6 systolic murmur. The liver was enlarged. The child was hypotonic. All reflexes were symmetric at 1+. Echocardiography demonstrated shift of the heart to the right, cardiomegaly, and increased pulmonary vascularity. Chest radiograph also showed cardiomegaly with questionable congestive failure. Laboratory examination was remarkable for persistent hypoglycemia. Cranial ultrasonography showed asymmetry of the hemispheres with an enlarged left hemisphere and displacement of the superior sagittal fissure to the right (Fig. 1). The left lateral ventricle was enlarged and irregular in outline. The left cerebral hemisphere showed an increase in echogenicity compared to the right. The sulcal pattern on the right ap· peared normal, whereas that on the left was markedly dimin~ ished to absent, suggestive of lissencephaly. The right lateral ventricle was not seen, presumably because it was com• pressed by the expanded left hemisphere. Several areas of increased echogenicity were seen around the left ventricle, possibly calcific in origin. Abnormal cerebral vessels were noted in the region of the straight sinus. Doppler examination showed increased diastolic flow, but no definite arteriovenous malformation was seen. CT scanning followed by cerebral arteriography was performed. CT confirmed the presence of an enlarged left hemisphere and left lateral ventricle with shift of the midline to the right. Abnormally decreased sulcation was seen on the left, with a deep sylvian fissure. A small intraventricular hemorrhage was seen in the left occipital hom. Marked asymmetry between the attenuation of the two hemispheres was seen, thought to be compatible with right-sided infarction. Several small foci of calcification were observed around the left frontal hom. Arteriography demonstrated large ca· rotid arteries, no arteriovenous malformation, and enlarged
© 1992 by the American Institute of Ultrasound in Medicine • J Ultrasound Med 11:563-566, 1992 • 0278-4297/92/ $3.50
564
UNILATERAL MEGALENCEPHALY
Figure 1 Coronal ultrasonogram shows enlarged left lateral ventricle. Note shift of midline, homogeneous parenchymal l!chogenicity of left hemisphere with decreased sulcation, and nonvisualization of right lateral ventricle with deep left syl~ vian fissure (arrow) . anomalous venous sinuses on the left, particularly with shift of the midline. There was increased perfusion of the left hemisphere with rapid shunting of blood into the deep venous system. The infant's hypoglycemia could not be controlled, and he died from hepatic and cardiac failure. An autopsy was per· formed. Enlargement of the left lateral hemisphere, left brainstem, and spinal cord were noted. Severe dysplasia of the cerebral cortex, basal ganglia, and thalami including hippocampus was found with hypoplasia of the corpus callosum. Sulcation was abnormal, with pachygyria. The left lateral ventricle was enlarged and had a small intraventricular hemorrhage. Focal calcifications were found within the periventrkular cortex. The vascular system findings corresponded to those seen at arteriography. Microscopic examination showed neuronal heterotopia and cytomega]y, as well as cortical disorganiza· lion, compatible with unilateral megalencephaly.
CASE2 The second case is an infant girl born at 39 weeks of gestation by cesarean section to a 28 year old gravida 3, para 1 mother. The pregnancy was uncomplicated. Prenatal ultrasonography had shown a large head and left hemisphere interpreted as porencephaly. At birth the head circumference was greater than the 97th percentile at 41 em. It was unusually shaped, with marked prominence on the left. Seizure activity was noted on the first day of life, with jerky eye movements. The seizures became generalized tonicAclonic with arching of the back and backward rolling of the eyes lasting for 5 to 10 seconds. Jnitial treatment with phenobarbital did not ade· quately controJ the seizure activity, so the patient was
J Ultrasound Med 11:563- 566, 1992
switched to Mocadon and ACTH. The patient had multiple admissions for seizure control and pneumonia, Progressive developmental delay was first noted at approximately 6 weeks of age, with poor head control. All deep tendon reflexes were 1+ with questionable upgoing toes. The patient reacted to pain in all limbs. There was mild hypotonia. The electroencephalogram (EEG) showed marked depression of background activity with moderate abnormal spikes seen. Radiologic investigations included cranial computed tomography (CT), sonography, and magnetic resonance (MR) imaging. All imaging modalities demonstrated left hemispheric enlargement with shift of the midline to the right, large ipsilateral lateral ventricle, and abnormal sulcation. Retrospective review of the prenatal sonograms also demonstrated the ventricular hypertrophy and abnormal sulca· tion with prominent sylvian fissure (Fig. 2A). Cranial sonog~ raphy showed periventricular focally increased echogenicity (Fig. 28) corresponding to the calcifications seen on CT. MR imaging exquisitely demonstrated the abnormal increased cortical thickness and poor gray versus white matter differ~ entiation (Fig. 2C).
DISCUSSION Unilateral megalencephaly, also known as hemimegalencephaly, shows variable severity from mild lobar enlargement to marked distortion of the entire cerebral and cerebellar hemispheres, ipsilateral brainstem, and, quite rarely, even spinal cord.'-' The clinical presenta tion typically is early onset of seizures (before 4 months of age), which are usually progressive and unilateral, intractable, and associated with developmental delay and abnormal head growth. The pathologic findings have been described previously and depend on the severity of the disorder, with the most extreme cases showing areas of lissencephaly, polymicrogyria, and a thickened cortex with poor separation of gray and white matter.• Microscopically there is generalized disorganization of all cortical layers with giant neurons and heterotopia.'-' Treatment with hemispherectomy has been recommended.' Radiographic findings have been reported previously from angiographic, CT, and MR imaging studies. 1 ~ 4 • 6 As in our cases, CT and MR imaging generally show marked enlargement of the entire involved hemisphere with contralateral shift of the midline structures and lateral ventricular enlargement ipsilaterally. Additional findings include decreased sulcation, diminished operculization, and cortical thickening or localized involvement of the occipitoparietal region.2. 3 Decreased density of the white matter also was noted in several patients on CT scans, whereas MR imaging shows poor gray and white matter differentiation. On angiography, straightening, stretching, and separation of vessels is seen related to the enlargement of the hemisphere. Vascular enlargement and increased 4
J Ultrasound Med 11:563- 566,
BABYN ET AL
1992
565
A
c
8
perfusion to the point of arteriovenous shunting are rare, with our case 1 and one other having had conges· tive heart failure. The only previous mention of cranial ultrasonog· raphy in this disorder described increased echogenicity of the involved hemisphere. 2 As the pathologic features of unilateral megalencephaly include lissencephaly, it is not surprising that the sonographic features bear some resemblance to those previously described for lissencephaly.5• 7 The abnormal sulcal pattern, secondary to failure of migration, persists after the third or fourth month. The widened subarachnoid space within the sylvian fissure and enlarged ventricle are easily seen on ultrasonography. The enlarged ventricle should not be confused with unilateral hydrocephalus or porencephaly. The asymmetry of cortical density on CT also is reflected in the change in echogenicity. Associated calcifications also can be detected. We believe the sonographic findings just described to be characteristic of unilateral megalencephaly, cor·
Figure 2 A, Prenatal ultrasonogram obtained at 34 weeks of gestation showing left hemispheric enlargement, ipsilateral ventricular enlargement, and prominent sylvian fissure (ar• row). B, Coronal ultrasonogram at the level of the frontal horn on the right shows left hemispheric enlargement with shift of the midline to the right and focal areas of increased echogenicity corre5ponding to calcifications on CT. The over· all echogenicity of the left hemisphere is Jess than that on the right. Note abnormal sulcal pattern along interhemi* spheric fissure (arrllw). C, Axial MR image showing similar features to the ultrasonograms, with thickened cortex, en$ Jarged left lateral ventricle, and poor differentiation of gray and white matter.
relating well with previous CT and MR reports. It is hoped this will allow earlier diagnosis, especially pre· natally, affording better counseling to the parents and treatment to the child, as hemispherectomy is best performed before 6 months of age. 1
REFERENCES 1. King M, Stephenson JB, Zievogel M, eta!: Hemimegalen·
cephaly- a case for hemispherectomy? Neuropediatrics 16:46, 1985
566
UNILATERAL MEGALENCEPHALY
2. Fitz CR, Harwood-Nash DC, Boldt OW: The radiographic features of unilateral hemimegalencephaly. Neuroradiology 15:145. 1978 3. Barkovich AJ, Chuang SH: Unilateral megalencephaly: Correlation of MR imaging and pathologic characteristics. AJNR 11:523, 1990 4. Kalifa G, Sellier N, Demange P, et al: Hemimegalence· phaly: MR imaging in five children. Radiology 165:29, 1987
J Ultrasound Med 11:563- 566, 1992
5. Raminez RE: Sonographic recognition of lissencephaly (agyria). AJNR 5:830, 1984 6. Walters BC, Burrows PE, Musewe N, et al: Unilateral megalencephaly associated with neonatal high output cardiac failure. Childs Nerv Syst 6:123, 1990
7. Cioffi V, Bossi MC, Ballarati E, et al: Lissencephaly in two brothers detected by US. A "pseudo-liver• pattern. Pediatr Radio! 21 :512, 1991
