Craniotomy
A craniotomy is a surgical procedure in which a section of the skull, known as a bone flap, is temporarily removed to provide access to the brain for diagnostic or therapeutic interventions.[1] This technique allows neurosurgeons to address various intracranial conditions, such as brain tumors, hematomas, aneurysms, vascular malformations, abscesses, and epilepsy, while aiming to preserve neurological function, with the bone flap typically replaced at the end of the surgery using plates and screws.[2] Performed under general anesthesia (or awake in select cases), craniotomy is a cornerstone of neurosurgery, often lasting several hours depending on the complexity of the underlying issue.[3] The practice of craniotomy has ancient origins, dating back to prehistoric times with trephination—drilling holes in the skull for ritualistic or therapeutic purposes, evidenced as early as 7000 years ago.[1] It was codified for treating skull fractures by Hippocrates in the 5th century BCE, and modern techniques evolved in the 19th century, with Wilhelm Wagner introducing temporary bone flap removal in 1889, leading to contemporary neurosurgical applications.[4]Introduction and Overview
Definition and Purpose
A craniotomy is a neurosurgical procedure involving the temporary removal of a section of the skull, known as a bone flap, to provide access to the underlying brain tissue for therapeutic or diagnostic interventions.[1] This bone flap is typically replaced and secured at the end of the procedure using plates, screws, or other fixation devices, allowing the skull to heal and resume its protective function.[2] The primary purpose of a craniotomy is to enable surgeons to treat various intracranial pathologies, alleviate elevated intracranial pressure, or obtain direct access for biopsies and other diagnostic evaluations.[1] Unlike a craniectomy, in which the removed bone is not replaced—often to allow for brain expansion in cases of severe swelling—a craniotomy preserves the structural integrity of the skull post-surgery.[2] It also differs from trephination, an ancient technique limited to creating a single small hole in the skull via drilling, whereas modern craniotomy involves multiple interconnected burr holes to form a larger, precise flap.[1] The skull, which the craniotomy targets, consists of dense cortical bone forming the outer and inner tables separated by a spongy layer called the diploe, providing robust protection to the enclosed brain while accommodating vascular and neural structures.[1] This layered composition allows surgeons to carefully navigate and preserve vascular supply during flap creation and replacement. In contemporary neurosurgical practice, craniotomies are conducted in specialized operating rooms equipped with advanced imaging and navigation systems, serving both elective procedures for planned interventions and emergency operations to address acute threats.[2]Historical Development
The practice of craniotomy traces its origins to ancient trepanation, a surgical technique involving the creation of holes in the skull, evidenced in prehistoric skulls dating back to the Neolithic period around 10,000 BCE. Archaeological findings reveal healed trephinations in skulls from various regions, including Europe and South America, indicating that patients often survived the procedure, which was likely performed to treat head injuries, relieve intracranial pressure, or for spiritual or therapeutic purposes such as exorcising evil spirits.[5][6] In the 19th century, significant advancements laid the groundwork for modern craniotomy. Joseph Lister introduced antiseptic techniques in 1867, using carbolic acid to reduce postoperative infections, which dramatically lowered mortality rates in cranial surgeries from over 40% to under 3% by the early 20th century. Building on this, Victor Horsley performed the first successful modern neurosurgical craniotomies in the 1880s, including excisions for epilepsy and tumors, establishing neurosurgery as a distinct field.[7][8] The 20th century brought further milestones in precision and safety. In the 1920s, Harvey Cushing collaborated with William T. Bovie to develop the electrosurgical unit, enabling effective hemostasis during brain operations and allowing access to previously inoperable tumors by minimizing blood loss. The 1960s saw Mahmut Gazi Yasargil pioneer microneurosurgery by integrating the operative microscope into cranial procedures, enhancing visualization and enabling intricate vascular anastomoses. By the 1970s, stereotactic guidance advanced with the invention of the N-localizer for CT-based targeting, improving accuracy in deep brain interventions.[9][10][11] Since the 1990s, craniotomy has evolved toward greater precision and reduced invasiveness. Intraoperative MRI, first implemented in neurosurgical suites in the mid-1990s, allows real-time imaging to guide resections and confirm completeness, particularly for tumors. The 2010s introduced robotic assistance, such as the ROSA system, which provides stereotactic planning and arm guidance for minimally invasive approaches, decreasing incision size and recovery time. Post-2000, the shift to keyhole and endoscopic techniques has further minimized tissue disruption while maintaining efficacy.[12][13][14]Indications
Medical Conditions Requiring Craniotomy
Craniotomy is a critical surgical intervention for numerous medical conditions that compromise brain integrity. These conditions span oncological, vascular, traumatic, infectious, and other pathologies, where the procedure provides direct access to the brain to address life-threatening pathophysiology such as mass effect, hemorrhage, or infection. Oncological ConditionsBrain tumors, including gliomas and meningiomas, frequently necessitate craniotomy due to their progressive growth, which exerts mass effect on surrounding neural tissue, elevates intracranial pressure, and induces neurological deficits like seizures or cognitive impairment.[1] The rationale for intervention is tumor resection to achieve debulking, which alleviates symptoms and pressure, or complete removal when feasible for curative intent, particularly in accessible low-grade tumors or metastases.[2] For instance, high-grade gliomas infiltrate brain parenchyma, compromising function, while meningiomas compress adjacent structures, both requiring surgical access to improve survival and quality of life.[15] Vascular Conditions
Vascular anomalies such as cerebral aneurysms and arteriovenous malformations (AVMs) demand craniotomy because of their propensity for rupture, leading to subarachnoid or intracerebral hemorrhage that causes rapid increases in intracranial pressure and potential herniation.[1] Pathophysiologically, weakened vessel walls in aneurysms or abnormal fistulous connections in AVMs disrupt normal blood flow, risking ischemia or bleeding; surgical exposure allows for clipping of aneurysms or resection/embolization of AVMs to prevent recurrent hemorrhage and stabilize hemodynamics.[2] Traumatic Conditions
Traumatic brain injuries, particularly those involving subdural or epidural hematomas and severe skull fractures, require urgent craniotomy as accumulated blood or bone fragments compress brain tissue, exacerbating edema and risking irreversible damage through ischemia or herniation.[1] The underlying pathophysiology includes vascular disruption from impact, leading to hematoma expansion that elevates intracranial pressure; evacuation via craniotomy relieves this compression, preventing secondary injury and facilitating recovery.[15] Depressed fractures with dural penetration further necessitate intervention to repair breaches and remove foreign bodies.[1] Infectious Conditions
Brain abscesses and subdural empyemas arise from bacterial invasion, forming encapsulated pus collections that expand, increase intracranial pressure, and propagate infection to adjacent meninges or parenchyma, potentially causing sepsis or focal deficits.[1] Craniotomy enables thorough drainage and excision of the abscess capsule or empyema, which is essential to eradicate the infectious source, reduce mass effect, and allow antibiotic penetration for resolution.[16] For empyemas, wide exposure via craniotomy ensures complete evacuation of purulent material, superior to limited burr hole approaches in complex cases.[17] Other Conditions
In certain complex cases, such as following decompressive craniectomy for post-traumatic hydrocephalus, craniotomy may be combined with ventriculoperitoneal shunt placement or revision where excess cerebrospinal fluid accumulation dilates ventricles, compressing brain tissue and impairing cognition or motor function.[18][19] The pathophysiology involves impaired CSF absorption or flow, leading to hydrocephalus ex vacuo post-injury; surgical access facilitates shunt insertion to normalize pressure. Craniotomy is also used for decompression in Chiari malformation, involving suboccipital bone removal to relieve brainstem compression, and for repair of CSF leaks at the skull base.[20] Epilepsy surgery via craniotomy targets epileptogenic foci in drug-resistant cases, where abnormal neuronal firing circuits cause recurrent seizures; resection disrupts these pathways to achieve seizure control.[21] Emerging applications include deep brain stimulation for Parkinson's disease, where craniotomy provides access for electrode placement in the subthalamic nucleus to modulate dysfunctional basal ganglia circuits, alleviating motor symptoms like bradykinesia.[22]