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tion. In this case, yearly follow-up imaging studies are done to assess tumor status. In summary, no single therapeutic modality is either ideal or unacceptable in the management of prolactinsecreting pituitary tumors. Fortunately, stage I and II tumors lend themselves to surgical cure, which avoids the need for a lifelong commitment to a medical regimen. The role of bromocriptine therapy adds a useful alternative to surgical intervention in some patients and also plays a crucial role in the combined management of more invasive lesions. The net result of this complementary set of therapeutic options is the reduction or elimination of tumor mass

and the restoration of normal endocrine function.

JOHN H. NEAL, MD

Orange, California

MARTIN H. WEISS, MD Los Angeles, California REFERENCES

Weiss MH: Treatment options in the management of prolactin-secreting pituitary tumors. Clin Neurosurg 1986; 33:547-552 Weiss MH, Wycoff RR, Yadley R, Gott P, Feldon S: Bromocriptine treatment of prolactin-secreting tumors: Surgical implications. Neurosurgery 1983; 12:640642

Surgical Treatment of Petroclival Meningiomas THERE HAS BEEN A dramatically increased interest in more aggressive surgical treatment of tumors at the base of the skull. New approaches are being developed, and old ones are being revitalized. Because of the complexity of the anatomy at the skull base, surgical approaches to this region are now frequently multidisciplinary, involving most often a neurosurgeon and an otolaryngologist. The team approach has provided tumor management that is more powerful than the sum of its parts, and nowhere is this more apparent than in the surgical treatment of meningiomas of the petrous bone and clivus, histologically benign lesions rendered malignant solely because of their relative surgical inaccessibility.

Petroclival meningiomas have been resected most commonly by the suboccipital (posterior fossa) retromastoid approach, and for most lesions this has been adequate. Surgical access to more complex lesions, however, such as those that extend to the prepontine cistern, middle fossa, or craniovertebral junction, require novel techniques often involving removing portions of the cranial base. Modern thinking stresses an approach that, while fundamentally a posterior fossa craniotomy, is different in that the sigmoid sinus is no longer the lateral limit to bone removal, such that a more direct line of vision along the petrous bone and in front of the cerebellum to the petrous apex and clivus is available to microsurgeons. This "petrosal" approach is now possible because the neurosurgery-neuro-otology team

is not reluctant to drill anteriorly into the temporal bone. There are three types of transpetrosal posterior fossa craniotomy: retrolabyrinthine, translabyrinthine, and transcochlear. In the retrolabyrinthine approach, bone removal anterior to the sigmoid sinus is halted at the level of the semicircular canals. Although this approach spares auditory function, it affords only a slightly improved access to the posterior fossa. In the translabyrinthine procedure, anterosigmoid bone is removed to the level of the internal auditory canal. This provides excellent visualization of the lateral aspect of the pons and upper medulla with only minimal retraction of the cerebellar hemisphere. Because the semicircular canals are removed, unilateral hearing loss is inevitable. In the-transcochlear approach, the entire otic capsule is removed along with the middle ear and external auditory canal. By anteriorly rerouting the facial nerve from

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its intratemporal canal and then resecting both the petrous apex and lateral aspect of the clivus, an unimpeded view of the ventral aspect of the pons and clivus is obtained without the need for brain retraction. Hearing loss and transient facial palsy are acceptable deficits only with an otherwise inaccessible and potentially lethal tumor. For tumors that arise high on the petrous bone and clivus, surgeons are adding a low temporal craniotomy to the petrosal approach with ligation of either the transverse or, more frequently, the superior petrosal sinus to allow splitting of the tentorium for additional superior exposure through the supratentorial space. For lesions arising from or extending to the low clivus or anterior rim of the foramen magnum, the lateral accentuation of the approach angle is gained by isolating and protecting the vertebral artery and drilling off the lateral aspect of the foramen magnum and occipital condyle. Because the sigmoid sinus sweeps anterosuperiorly at this level, drilling can be safely carried forward all the way to the hypoglossal canal. For these same low clival or anterior foramen magnum meningiomas, some surgeons are attempting an anterior (transoral, transclival) approach. Despite the development of fibrin glues for dural repair, however, the specter of postoperative cerebrospinal fluid leak into the oropharynx makes most surgeons reluctant to remove intradural lesions by this route. Certain petroclival meningiomas will not be completely resectable despite the aforementioned advances in surgical access. For them, external radiation therapy, brachytherapy, and radiosurgery will be useful treatment adjuncts. PHILIP H. GUTIN, MD ROBERT K. JACKLER, MD San Francisco, California REFERENCES

Al-Mefty 0, Fox JL, Smith RR: Petrosal approach for petroclival meningio-

mas. Neurosurgery 1988; 22:510-517 George B, Dematons C, Cophignon J: Lateral approach to the anterior portion of the foramen magnum-Application to surgical removal of 14 benign tumors: Technical note. Surg Neurol 1988; 29:484-490 Giannotta SL, Pulec JL, Goodkin R: Translabyrinthine removal of cerebellopontine angle meningiomas. Neurosurgery 1985; 17:620-625 Miller E, Crockard HA: Transoral transclival removal of anteriorly placed meningiomas at the foramen magnum. Neurosurgery 1987; 20:966-968

Intraoperative Digital Subtraction Angiography for Neurosurgery HIGH-RESOLUTION, REAL-TIME, digital subtraction angiography (DSA) facilitates the intraoperative management of complex intracranial vascular disorders. Portable DSA equipment is now available that provides angiographic images virtually equivalent to conventional angiography. A mobile "C" arm fluoroscopy unit with high-resolution video is fitted with frame-averaging, catheter road mapping and automatic peak opacification capability. These features reduce the volume of contrast material necessary for adequate images. The system is powered by standard 115-volt, 20-ampere lines and requires no special shielding. The software package can be modified to allow for stereoscopic visualization of intracranial vascular lesions. Angiographic pictures accrue immediately, with the advantage of overlying bony and relatively radiopaque instrument subtraction. Carbon-fiber head holders can be subtracted, but ordinary metal instruments cannot. Draping, scalp hemostasis, and retraction require modification to avoid metallic artifacts. Technical considerations involved in intraoperative transfemoral or direct arterial catheterization have been described. Indications for intraoperative neurosurgical DSA are di-

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agnostic, therapeutic ("interventional"), or a combination of both. The obvious benefit of immediate intraoperative angiographic information is the ability to promptly and precisely improve therapeutic maneuvers. Arteriovenous malformations and fistulas, complex aneurysms, arterial occlusive disease, and hemorrhage localization compose the majority of lesions studied intraoperatively with DSA. The procedure does prolong operative time, so use is ordinarily reserved for more difficult intracranial vascular procedures. The incidence of technical surgical problems diagnosed by intraoperative angiography is significant. In one series, 7 of 32 procedures required intraoperative modification and in another series, 7 of 33. These relatively high rates are ascribable to the selection of difficult cases for treatment and study. The principal technical surgical problems detected include incomplete aneurysm clipping or arteriovenous malformation resection and unintentional vessel occlusion. These problems were corrected intraoperatively and confirmed by DSA. There have been no reports of major complications of DSA when the indications are clearly for diagnostic purposes. Intraoperative DSA affords new options for treating inaccessible vascular lesions. Neurosurgeons can expose vessels otherwise inaccessible by catheter for the purpose of embolization, balloon occlusion, or angioplasty with the advantage of an immediate determination of the efficacy of the procedure. The progressively improving imaging capability of DSA, coupled with the mutual interests of neurosurgeons and neuroradiologists, is clearly resulting in an improved outcome for patients with difficult and challenging intracranial vascular disorders. WOLFF M. KIRSCH, MD Y. H. ZHU, MD Loma Linda, California

REFERENCES

Bauer BL: Intraoperative angiography in cerebral aneurysm and AV-malformation. Neurosurg Rev 1984; 7:209-217 Hieshima GB, Reicher MA, Higashida RT, et al: Intraoperative digital subtraction neuroangiography: A diagnostic and therapeutic tool. AJNR 1987; 8:759767

Irritable Children ACUTE IRRITABILITY IN A CHILD is commonly due to an infection such as an upper or lower respiratory tract infection or gastroenteritis; a gastrointestinal disorder, such as a milk allergy or intolerance, appendicitis, intussusception or hernia; or trauma, especially inapparent fractures. Fever, dehydration, decreased food intake, pain, or sleep disturbances frequently worsen the degree of irritability. Chronic irritability may be due to a much broader range of pediatric illnesses that encompass chronic infection; endocrine and renal diseases; anemia, leukemia, and other such disorders; colic; parenting problems; neglect; abuse; and substance or toxin exposure. An overview of the common medical, surgical, and orthopedic causes of irritability is provided in several of the standard textbooks on pediatrics and critical care. Emergency department physicians, family practitioners, or pediatricians, however, are confronted with other situations in which a child is irritable, yet no apparent reason can be determined. It is important, then, to realize that approximately 35% of children are seen in emergency departments because of neurologic problems. By considering the following, the need for further timely neurosurgical or neurologic consultation can be decided. In general, a suspicion of central nervous system infection warrants an immediate evaluation that includes a lum-

bar puncture and, depending on the severity of symptoms, computed tomographic (CT) or magnetic resonance imaging (MRI) scanning and early antibiotic treatment. An irritable infant with a tense fontanel could have a subdural effusion, empyema, acute hydrocephalus, cerebral edema, or abscess, all of which require early and different neurologic and neurosurgical treatments. Nonaccidental trauma from the shaking of infants is a frequent cause of unexplained irritability. A careful examination by a neurologist or neurosurgeon can detect retinal or subhyaloid hemorrhages, nuchal rigidity, hyperreflexia, and corticospinal tract involvement signaling the need for further diagnostic tests such as CT or MRI scanning and lumbar puncture. In a patient with multiple trauma with limited or no initial central nervous system symptoms, the later occurrence of irritability may not be related to systemic injury and pain. An evaluation to rule out an epidural, subdural, or subarachnoid hemorrhage should be considered. Mastoiditis can also result from a delayed diagnosis of otitis media, and when neurologic symptoms appear, they may be due to septic thrombosis of the transverse sinus. In an irritable infant or child, signs of increased intracranial pressure such as papilledema, ophthalmoplegia, or abnormal pupillary reflexes are difficult for most physicians to assess, yet may be critical in establishing a specific diagnosis and deciding on the type of scan-CT versus MRI-to do to yield the maximal information for the most reasonable cost and safety to the patient. As greater efforts are made to contain the costs of hospital care, consultation by a neurosurgeon or neurologist in such emergency situations may obviate the need for unnecessary studies and direct the evaluation toward the most timely study with the most useful information. Irritability alternating with lethargy is a common postictal or toxic-metabolic manifestation in children. This may be due to either acute seizure activity or medication side effects, such as phenobarbital or primidone, in a child with a seizure disorder. Determining anticonvulsant drug levels and obtaining an electroencephalogram, a urine toxicology screen, and a consultation may clarify the cause of a child's irritability. Symptoms such as head tilt, diplopia, or vomiting are associated with tumors of the nervous system, which are the most common form of solid neoplasms of infancy and childhood. Wryneck may also be a sign of atlantoaxial rotary subluxation. Nuchal rigidity without fever may be caused by subarachnoid hemorrhage from a small arteriovenous malformation that has ruptured. If the child is known to have a preexisting neurosurgical disorder, the general practitioner or pediatrician should still proceed with an organized workup and obtain consultation, especially if actual manipulation or tapping of a shunt is indicated. Measuring the child's head circumference and plotting trends on appropriate charts provide useful and complementary information to that obtained from radiographic studies. By addressing these issues, primary care physicians can then make a reasonable decision as to whether specialty consultation may be warranted for further evaluation and management. There are also several excellent reference sources available. DAVID KNIERIM, MD STEPHEN ASHWAL, MD Loma Linda, California

REFERENCES

Fleisher GR, Ludwig S: Textbook of Pediatric Emergency Medicine, 2nd ed. Baltimore, Md, Williams & Wilkins, 1988