The management of epileptic seizures in pediatrie and adolescent practice is generally nonsurgical. Anticonvulsant medication effectively controls seizures in about 75 per cent of patients. Whether or not seizures are controlled by medication, they may possibly be secondary to an intracranial lesion such as tumor, subdurai hematoma, abscess, or vascular malformation. Although the likelihood of having such a lesion is relatively small, it is important to identify these patients as early as possible in order for them to benefit maximally from surgical treatment.
Most patients with seizures are regarded as having symptomatic epilepsy, that is, epilepsy secondary to some structural abnormality. The exact etiology, however, is difficult to determine in a high percentage of cases. Neurosurgical management may be essential for patients in whom a life-threatening or other progressive lesion has been identified, such as intracranial neoplasm or hematoma. In some cases in which a space-occupying lesion has been reasonably well excluded, the clinical features may suggest a nonprogressive or static brain lesion, such as a post-traumatic scar which may produce an irritative epileptogenic focus. In cases of nonprogressive lesions, surgical intervention is considered only in patients in whom disabling seizures persist despite adequate trials on anticonvulsant medication.
Seizures Secondary to Progressive, Sometimes Life-threatening, lntracranial Lesions: Neurosurgical Intervention (orClose Observation)Essential
Fifteen per cent of children have seizures within the first week after closed head injury; a large majority of these occur within the first two hours.1 The occurrence of one or more seizures in the early post-traumatic period is not a reliable indicator of the presence or absence of complications such as intracranial bleeding. Declining level of consciousness and neurologic signs, asymmetrical re Hexes or hemiparesis, are critical features.
After the first week, the occurrence of seizures drops significantly to a range of O to 4 per cent during the succeeding years (Figure 1). Although the overall number of patients affected by late post-traumatic seizures is very low, the risk is greater in children who had one or more early seizures than in those without any early fits.1 The risk of recurrent seizures is highest during the first year after injury. Prophylactic anticonvulsant medication for at least one year is therefore advisable for a child who has had any early post-traumatic seizures.
Epileptic children and sports. The question sometimes arises whether children with a history of seizures should be permitted to engage in contact sports. As far as is known, these children do not differ from nonepileptics in their risk of early posttraumatic seizures.
Chronic subdural hematoma. Bleeding from tears in bridging veins in the subdural space, even after mild head injuries, may occur in children of all ages but is most common during the first two years of life. A clear-cut history of head trauma is often lacking. Convulsions occur in over half the cases and may be associated with other nonspecific features such as vomiting, fever, failure to thrive, bulging anterior fontanelle, or hyperactive deep tendon reflexes. Helpful clues include retinal hemorrhages, or prominence of the parietal areas of the head, as distinguished from the bulging of the frontal regions which occurs in hydrocephalus. Bilateral puncture of the subdural space through the coronal suture should be carried out in any baby in whom the diagnosis is suspected.
Brain tumors are relatively common neoplasms in children, being exceeded in frequency only by the leukemias and the renal-suprarenal tumors. Although seizures in children are rarely due to brain tumors, 16 per cent of children with brain tumors present with seizures.2 The tendency for seizures is higher (25 per cent) in patients with tumors in the supratentorial space, which are more likely to cause cortical irritation, than in patients with infratentorial (posterior fossa) tumors. In children, infratentorial tumors are more frequent than supratentorial neoplasms. Those in the posterior fossa, however, cause earlier obstruction of the cerebrospinal fluid (CSF) pathways, leading to the rapid development of increased intracranial pressure and hence to earlier diagnosis. Slow-growing tumors in the supratentorial space commonly fail to cause clinically evident brain compression or CSF obstruction until the late stages, often resulting in an unfortunate delay of diagnosis of two years or longer after an initial seizure.3
Identification of "tumor suspects." In contrast to the more common association or seizures and brain tumors in adults, epilepsy beginning in childhood or adolescence is only rarely associated with cerebral tumor. Despite this encouraging statistical perspective of the problem, the clinician is faced with the need to identify the small but important group of children whose seizures are manifestations of cerebral tumor. Early detection, when the tumor is relatively small and accessible, can make a significant difference in the results of surgical treatment.
Figure 1. Occurrence of posl-lraumatic seizures in a group of 301 head-injured children, "n" refers to the number of children, from the - original group of 301, examined at each interval.
NDICATIONS FOR NEUROSURGICAL DIAGNOSTIC STUDIES
Since the type of seizures in these patients varies widely, seizure-pattern is of little diagnostic help. Apart from the neurologic examination (including optic fundí), the electroencephalogram (EEG) is an invaluable diagnostic screening tool. Serial EEG tracings may be of localizing or lateralizing value in supratentorial tumors. In patients with expanding lesions in the posterior fossa, the EEG abnormalities tend to be maximal in the occipital regions.
Plain skull films should also be carried out in most patients with recurrent seizures. Common skull film abnormalities seen in patients with brain tumors include separation of the cranial sutures, localized erosion of bone, and localized cerebral calcification.
In following a patient with chronic seizures, especially if there is a change in seizure pattern or frequency, it is important to repeat the neurologic examination, as well as the EEG and skull films, at intervals. A subtle clinical feature which should alert the clinician to the possibility of a spaceoccupying lesion is the report from the parents of a behavioral change or deterioration in school performance. This history, or the appearance of a focal neurologic deficit, should prompt repeat EEG and skull films and consideration for further neurosurgical diagnostic study. Although progressive neurologic deficit is the clearest indication for special neurosurgical studies, other factors also contribute to the decision. One or more of the factors listed in Table 1 may point to the desirability of further study.
Figure 2. EEG recording from the brain (electrocorticography) prior to temporal lobectomy.
Tuberous sclerosis. Cerebral involvement in this condition is associated with mental retardation, seizures, and, quite commonly, facial skin lesions (adenoma sebaceum). Cerebral nodules, probably a form of glioma, are found in the cortex or as subependymal nodules which bulge into the ventricular system. The paraventricular lesions, identified on plain skull films by calcification, require neurosurgical intervention if they produce ventricular obstruction.
Neurosurgical diagnostic studies. Isotope brain scans are safe and carry a high degree of accuracy in identifying brain tumors and brain abscesses. Occasional false negatives do occur in low-grade gliomas and other relatively benign tumors, particularly in the parasellar region. Cerebral arteriography and air studies (pneumoencephalography or ventriculography) add significantly to the accuracy of tumor localization. In some slow-growing neoplasms, even these studies may prove initially negative (especially in the temporal lobes) and may have to be repeated at a later date before the diagnosis can be confirmed.
Figure 3. Right temporal lobectomy for intractable psychomotor seizures. Note surgical defect in anterior temporal region (arrow).
Brain abscess. Although antibiotics for childhood infections such as mastoiditis have reduced the frequency of brain abscess, in recent years there has been an increase in the number of brain abscesses related to the higher number of children surviving cyanotic congenital heart disease. The incidence of brain abscess as a complication of congenital heart disease has been estimated at three to five per cent; convulsive seizures may occur as an early manifestation. Except during the first two years of life, when brain abscess is relatively uncommon/ this diagnosis is seriously considered in patients with congenital cyanotic heart disease presenting with headache, convulsive seizures, or focal neurologic abnormality. Fever or evidence of systemic or local infection elsewhere in the body may be absent.
Isotope brain scanning is the single most useful diagnostic aid, although EEG is also helpful. Lumbar puncture may be performed to rule out meningitis, but lumbar puncture is best avoided in the presence of increased intracranial pressure (especially if associated with focal neurologic deficit), because of the hazard of cerebral herniation.
Although antibiotics have been shown to penetrate brain abscesses, the organisms are protected by the purulent milieu. Surgical aspiration or excision of the abscess is therefore essential.5 Intravenous antibiotic therapy is given in the pre- and postoperative period to prevent extension of infection and to control residual local infection after surgical evacuation of the abscess. High blood levels of penicillin or its derivatives may precipitate seizures. This risk can be minimized by careful regulation of the rate of intravenous drip in order to avoid sudden rises in penicillin blood level. Up to 50 per cent of patients have chronic seizures after surgery for brain abscess, but these can usually be controlled by anticonvulsant drugs.
Postmeningitic subdural effusion. Seizures are among the clinical features which suggest the accumulation of a subdural effusion in infants with bacterial meningitis. Diagnosis and treatment are achieved by bilateral subdural taps. Occasional cases may require surgical stripping of subdural membranes.
INTRACRANIAL VASCULAR MALFORMATIONS
Arteriovenous malformations. These congenital lesions of the brain may become manifest at any time from early infancy to adulthood. There is a tendency to repeated spontaneous intracranial hemorrhage; when mild, the bleeding is characterized by headache, transient neurologic deficit, neck stiffness, or seizure. Epileptic seizures commonly also occur independently of hemorrhage, presumably due to focal cortical scarring or ischemia. The EEG may point to a focal disturbance slow wave, spiking, or sharp wave), with corresponding abnormal isotope uptake on brain scan. The lesion and the question of its operability are best defined by cerebral arteriography.
Sturge-Weber syndrome. This is a congenital neurocutaneous condition consisting of cutaneous angioma of the face and venous angiomatosis of the cerebral pia-arachnoid, predominantly involving the occipital lobe. Seizures represent the main clinical problem. Intracranial bleeding is rare. In severe cases, neurologic deficits such as hemiparesis and behavioral deterioration occur, presumably due to progressive cerebral damage from hypoxia. Cortical calcification in adjacent gyri produces a characteristic "railroad track" pattern on skull films. Surgical resection of damaged cortex is considered when seizures are poorly controlled on medication or to prevent further behavioral deterioration.3 Hemispherectomy may be considered in cases of extensive unilateral cortical damage.
PROGRESSIVE DEGENERATIVE DISEASES
A variety of degenerative diseases of the brain, particularly of the neuronal storage type, are commonly associated with seizures. When other diagnostic or therapeutic measures have been exhausted, brain biopsy, usually in a "silent" area of frontal lobe, may be of value in identifying the process. Although therapy for most degenerative disorders is still limited, histologie diagnosis by brain biopsy permits prognostication. This is important in the total management of the child and may be of benefit in genetic counseling of the family.
Seizures Due to Nonprogressive or Static Brain Lesions: Surgical Intervention Considered in Selected Cases
TEMPORAL LOBE EPILEPSY
This complex form of epilepsy, also known as "psychomotor epilepsy," is one in which the abnormal neuronal discharges originate from one or both temporal lobes. Although this type of epilepsy is relatively uncommon in children, its recognition is important for proper selection of anticonvulsant medication and because some patients who are unresponsive to medication may be helped by surgical intervention. The seizures usually have their onset in older children, although they may begin in early childhood.6' 7
The attacks are characterized by a wide variety of motor, sensory, or behavioral disturbances which may not be identified as seizures until the recurring pattern is recognized. The attack pattern tends to change as the child becomes older. Premonitory symptoms of irritability or headache may precede a seizure by hours or days or there may be an aura described as abdominal discomfort, sudden fear, or an unpleasant smell or taste just before the attack. The ictus itself may be manifested by complex motor patterns (automatism) such as fumbling with clothing, kicking, or aggressive behavior, and is often associated with peculiar posturing or twitching of the body, lip smacking, or blinking of the eyes.
Mental or psychic characteristics of the seizure may include varying degrees of altered consciousness. After the attack, which may last several minutes, there is often sleepiness or confusion. These psychomotor seizures may occur alone or may be combined with other types of seizures such as generalized convulsions (grand mal). Because treatment differs in the two conditions, it is important to distinguish temporal lobe seizures from the abrupt onset and offset of the brief (10 to 15 seconds) absence fits of petit mal epilepsy, in which there is neither an aura nor post-ktal phenomena.
Pathogenesis. In patients in whom a space-occupying lesion such as tumor has been excluded by appropriate diagnostic studies, the psychomotor seizures are usually due to an atrophie lesion in the temporal lobe, the etiology of which remains in question.7' 8 When the lesion (mesial temporal or Ammon's horn sclerosis) affects the particularly vulnerable amygdala and hippocampus, the process has been said to be due to cerebral anoxia accompanying incidents such as febrile convulsions or status epilepticus in infancy.7 More diffuse damage to the temporal lobe is known to occur after meningitis, encephalitis, birth injury, or head injury. In some patients, no definite histologie lesion can be demonstrated.
Natural course of temporal lobe epilepsy. Most children can be controlled on drugs, and the majority "grow out of their seizures" as adolescence is approached." A small but therapeutically difficult minority continues with intractable seizures, and in about half of these, there is associated progressive behavioral and educational deterioration. It is this small group of children that may be considered for surgical therapy.
EEG. A unilateral temporal spike focus is generally an essential criterion in the decision regarding surgical intervention. In children who would otherwise be regarded as surgical candidates, but whose electrical findings are either normal, multi-focal, or nonspecific, depth electrodes may be implanted in the frontal and temporal regions for chronic recording. This often permits more precise localization of a discharging focus and may lateralize the predominant side in cases of bi-temporal spiking. These factors play an important role in determining whether the patient may be helped by surgery. Additional considerations in patient selection are listed in Table 2. Temporal lobectomy (Figures 2 and 3). Resection of the temporal lobe is restricted to the anterior temporal lobe on the side of the discharging focus and includes the amygdala and anterior hippocampus. In some cases, amygdalectomy alone may suffice. EIectrocorticography is carried out prior to the resection for final determination of the electrically abnormal area. In the dominant hemisphere (determined in doubtful cases by preoperative intracarotid injection of sodium amobarbital9), the temporal lobe resection must be more limited in order to prevent encroachment of the speech areas.
Results of surgery. Most of the experience with temporal lobectomy has been in adults. Excellent benefit has been achieved in terms of seizure and behavioral improvement in 50 per cent of patients, moderate improvement in 25 per cent, and no improvement in the remainder.10 The results have been equally encouraging in the smaller number of children and adolescents operated thus far.3, 7
Some degree of homonymous hemianopia, usually only a partial quadrantic defect, may occur as a side effect of temporal lobectomy. Intelligence, as measured by standard tests, remains unchanged, but specific memory deficits occur. After removal of the anterior temporal lobe from the left dominant hemisphere, there is some verbal memory loss, despite preservation of the speech areas. A corresponding temporal lobe removal from the right, nondominant hemisphere leaves verbal memory intact but impairs the recognition and recall of nonverbal visual and auditory patterns.10
The anticipation of these side effects is taken into account in considering a patient for temporal lobectomy. Compared, however, with the striking benefits which can be achieved, surgical deficits are probably a reasonable price for patients whose prospects for psychological and social adjustment are otherwise dismal.
OTHER FOCAL EPILEPSIES
As in the temporal lobe variety of focal epilepsy, the location of an abnormally discharging focus elsewhere in the brain may be determined by the clinical and EEC manifestations. If a progressive lesion such as tumor has been excluded by appropriate diagnostic study, the indications for surgical resection of the epileptogenic region are essentially the same as those outlined for temporal lobectomy (Table 2). An additional criterion is that the removal of the abnormal area of brain would not leave the patient with serious speech, intellectual, or neurologic deficit. At the time of surgery, the extent of resection is determined by the gross appearance of the cortex and by cortical EEG recording. Gyrectomy results in improvement in about 35 per cent of patients; if the involved cortex is near the pole of the frontal or occipital lobe, the lobe is resected back to normal tissue, which yields excellent results in approximately 50 per cent of cases.12
Infantile hemiplegic with epilepsy. Extensive damage to one cerebral hemisphere from trauma or infection early in life may result in residual contralateral hemiparesis. Focal seizures originating in the damaged hemisphere and severe behavioral disturbances may also occur, and there may be some degree of mental retardation. When the seizures or behavioral disorder are severe and unresponsive to medication, the surgical removal of the damaged hemisphere (leaving thalamus and other thencephalic structures intact) results in excellent seizure and behavioral control in 90 per cent of patients.11,13
If the hemiplegia or hemiparesis has dated from infancy, speech is usually preserved after hemispherectomy, regardless of the side of the brain involved. There is usually no increase in the motor deficit; in fact, motor function on the hemiparetic side may be slightly improved, presumably from the lessening of spasticity.
TEMPORAL LOBE EPILEPSY: INDICATIONS FOR SURGERY
Apart from the failure to respond to drugs, criteria for selection of patients for hemispherectomy include the requirement that the child has poor motor control and sensation in the fingers and hand on the hemiparetic side, as well as homonymous hemianopsia. Clinical, psychometric, and EEG evidence should also indicate that function of the other hemisphere is intact. Most patients have been operated during adolescence, but the procedure may be considered in younger hemiparetic children whose epileptic and behavioral disturbance represents a severe handicap.
Although seizures in childhood and adolescence are only occasionally of neurosurgical significance, it is important to identify those patients for whom surgical intervention may be indicated. From the neurosurgical standpoint, patients with seizures may be divided into two broad categories:
1. Seizures secondary to progressive, sometimes life-threatening, intracranial lesions, such as neoplasm or brain abscess, which require early neurosurgical evaluation. The appearance of a focal neurologic deficit (especially if progressive) or behavioral change suggests the need for EEG and skull films and possibly further diagnostic study.
2. Seizures due to nonprogressive or static lesions, such as focal cerebral scars or atrophy. This diagnosis may be tentatively assumed after appropriate diagnostic study has reasonably excluded a progressive lesion such as tumor. The diagnostic studies may have to be repeated at intervals. Surgical intervention may be considered in some of these patients in whom the seizures fail to respond to adequate trials of anticonvulsant medication. Gyrectomy, lobectomy, or hemispherectomy may yield gratifying benefit in carefully selected epileptic children or adolescents whose outlook for psychological and social adjustment otherwise appears hopeless.
1. Black, P., Shepard, R. H., and Walker. A. E. A prospective study of posttraumatic seizures in children. Trans. Amer. Neural. Assoc. 97 (1972), 247-250.
2. Backus, R. E. and Millichap, J. G. The seizure as a manifestation of intracranial tumor in childhood. Pediatrics 29 (1962), 978-984.
3. Maison. D. D. Neurosurgery o! Infancy and Childhood. Second Edition. Springfield: Charles C Thomas, 1969.
4. Tyler. H. R. and Clark, D. B. Incidence of neurological complications in congenital heart disease. Arch. Neural. Psychiat. 77 (1957). 17-22.
5. Black, P.. Graybill, J. R., and Charache. P. Penetration of brain abscesses by systemically administered antibiotics. J. Neurosurg. 35(1973), 705-709.
6. Chao. D., Sexton, J. A., and Pardo. L S. S. Temporal lobe epilepsy in children. J. Pediat. 60 (1962). 686-693.
7. Falconer, M. A. Significance of surgery for temporal lobe epilepsy in childhood and adolescence. J, Neurosurg. 33 (1970), 233-252.
8. Earle, K. M., Baldwin, M., and Penfield. W. lncisu ral sclerosis and temporal lobe seizures produced by hippocampal herniation at birth. Arch. Neurot. Psychiat. (Chic.) 69 (1953), 27-42.
9. Wada, J. A new method for the determination of the side of cerebral speech dominance. Med. Biol. 14 (1949), 221-222.
10. Walker, A. E. Man and his temporal lobes. John Hughlings Jackson Lecture. Sutg. Neurol. i (1973), 69-79.
11. Milner. B. Disorders of learning and memory after temporal lobe lesions in man. Clin. Neurosurg. 19 (1972). 421-446.
12. Walker, A. E. Operative Treatment of Epilepsy. W. T. Mustard. M. M. Ravitch, W. H. Snyder, Jr., K. J. Welch, and C. D. Benson, eds. In Pediatrie Surgery. Chicago: Year Book Medical Publishers. 1969.1572-1574.
13. Rasmussen, T. and Gossman. H. Epilepsy due to gross destructive brain lesions. Results of surgical therapy. Neurology 13 (1963). 659-669.
NDICATIONS FOR NEUROSURGICAL DIAGNOSTIC STUDIES
TEMPORAL LOBE EPILEPSY: INDICATIONS FOR SURGERY