Most readers benefit from reviewing the Quick Summary together with the sections on Warning Signs After Surgery, Brain (Parenchymal) Complications, and When a Second Opinion Is Appropriate. The remaining sections provide more detailed clinical explanations.

You can quickly find topics on this page by using your browser search (Ctrl+F), for example: CSF leak, hydrocephalus, bleeding/hematoma, stroke, seizures, infection, bone flap, pneumocephalus.

What Is a Craniotomy?

A craniotomy is a neurosurgical procedure in which a temporary opening is created in the skull to allow access to the brain, its coverings, or surrounding structures. The bone flap that is removed is usually replaced at the end of surgery and secured with plates or sutures.

It is performed to treat conditions such as:

• Brain tumors
• Intracranial hemorrhage
• Vascular malformations (AVM, aneurysm)
• Brain abscess
• Traumatic brain injury
• Epilepsy (selected cases)
• Cranial nerve compression

In the following sections, we will outline the stages of a craniotomy and the surgical management of pathological brain processes. This will provide a clearer understanding of how and why surgical complications can arise during different phases of the procedure.

Image: The image illustrates a craniotomy. Both the skin incision and the skull opening are performed within the hair-bearing area of the scalp. The dura is opened to expose the brain as part of the surgical approach to the tumor or other brain pathology. After the procedure, the bone flap is secured and the scalp is reconstructed, ensuring no cosmetic defect remains after healing.

Planning the Incision and Type of Craniotomy

Every craniotomy is individually planned based on:

• Location, size and type of the pathological process
• Its relationship to functional brain areas
• Proximity to arteries, veins, cranial nerves
• Depth and expected surgical corridor
• best cosmetic effects (performed within the hair-bearing area of the scalp)

Skin Incision

The scalp incision may be:

• Linear
• Curvilinear
• Horseshoe-shaped
• Question-mark shaped (common in trauma and large exposures)

The incision is designed to preserve blood supply and allow safe exposure while minimizing cosmetic impact.

Types of Craniotomy

The name of a craniotomy usually reflects the anatomical region of bone removal.
Patients may encounter these terms in operative reports, discharge summaries, or follow-up imaging reports.

Common types include:

• Frontal craniotomy
• Temporal craniotomy
• Parietal craniotomy
• Occipital craniotomy
• Pterional craniotomy
• Retrosigmoid craniotomy
• Bifrontal craniotomy
• Suboccipital craniotomy

Image: Common types of craniotomy and their anatomical names.

Opening the Skull and the Dura

After reflecting the scalp and controlling bleeding from the soft tissues:

1. Burr holes are created in the skull.
2. The bone flap is removed.
3. The dura mater (the protective membrane covering the brain) is exposed.
4. The dura is opened carefully in a planned fashion to access the surgical target. The dura is often opened in a curvilinear or cruciate pattern to allow later watertight closure.

Surgical Corridor: Reaching the Brain Pathological Process

The pathological process may be located:

• In the subarachnoid space (e.g., aneurysm, vascular malformation)
• On the brain surface
• Within the brain parenchyma (tumors, abscess)
• Adjacent to cranial nerves
• Near major arteries or veins

Whenever anatomy allows, surgeons use natural corridors — particularly the subarachnoid (SA) spaces and existing brain folds — to access the lesion while minimizing disruption of healthy tissue. If the lesion is extra-axial (outside the brain tissue itself), it can often be reached predominantly through these natural spaces, reducing the need to pass through functional brain tissue.

In contrast, when the pathological process is intra-axial (located within the brain parenchyma), direct access to the lesion may require a carefully planned cortical entry. This can involve:

• Gentle separation of natural sulci
• A limited, precisely placed corticotomy (small opening in the brain surface)
• Controlled passage through non-functional or strategically selected cortical areas

In certain cases, the surgical corridor combines both approaches — partly through subarachnoid spaces and partly through brain tissue — depending on depth and anatomical relationships.

Throughout this process, microsurgical techniques are used to preserve arteries, veins, perforating vessels, and critical neural pathways.

Working on the Brain Pathological Process

In the case of a tumor or infection (e.g., abscess), the procedure may involve:

• Internal debulking of the tumor or aspiration of pus in the abscess, or cyst
• Careful separation from surrounding healthy brain. However, not all lesions have clear anatomical boundaries. Adherent tumors, inflammatory processes, or vascular malformations may obscure the distinction between pathological and healthy tissue, increasing the technical complexity of safe removal.
• Identification and preservation of arteries and veins that may run directly adjacent to or even through the pathological process
• Protection of functional brain areas (motor cortex, speech centers, visual pathways) that may lie immediately next to the lesion
• Preservation of cranial nerves that may be compressed, displaced, or adherent to the tumor or vascular malformation

Important Surgical Reality

During this stage:

• Brain tissue may be injured by necessary manipulation.
• Adherent tumors may require careful peeling from arteries or veins.
• Small but important (perforating) arteries may be at risk.
• Temporary retraction can cause local pressure.
• Circulatory disturbance may occur.

If blood supply is compromised, this may lead to:

• Local ischemia
• Edema
• Delayed neurological worsening

Even when performed correctly, surgery in eloquent areas carries inherent risk.

The balance is always between removing pathology and preserving function.

Causes of Complications After Craniotomy and Open Brain Surgery

Complications after craniotomy and open brain surgery rarely arise from a single isolated cause. In most cases, they result from an interaction of multiple factors related to the disease, the patient, the surgical environment, and postoperative physiological changes. Not every postoperative event represents surgical error. Some complications reflect unavoidable biological risk associated with the disease itself.

Understanding this multifactorial nature is essential before drawing conclusions about why a complication occurred.

1. The Underlying Pathological Process

Some risks are inherent to the disease itself. In these situations, the surgical field may already be biologically unstable. The pathology itself can increase the risk of bleeding, vascular injury, postoperative swelling, or neurological deterioration. In certain locations, especially within eloquent brain areas, even minimal manipulation may carry functional risk.

Examples include:

• Highly vascular tumors – tumors rich in blood vessels increase the risk of intraoperative bleeding and postoperative hematoma formation.
• Deep intra-axial lesions – lesions located deep within the brain require passage through normal tissue, increasing the risk of neurological deficit.
• Large mass effect with surrounding edema – significant compression and swelling make tissue more vulnerable to additional surgical manipulation and postoperative swelling.
• Inflammatory or infectious processes – inflamed tissue is fragile, hypervascular, and often poorly demarcated from healthy brain, raising the risk of bleeding or incomplete separation.
• Lesions adherent to arteries, veins, or cranial nerves – when pathology is tightly attached to critical structures, safe separation may be technically challenging and carries risk of vascular or nerve injury.
• Pre-existing hemorrhage or tissue compromise – previously damaged or ischemic brain tissue may tolerate surgical manipulation less well and be more prone to postoperative deterioration.

2. The Condition of Surrounding Tissue and Patient Factors

The biological condition of the patient and local tissues significantly influences complication risk.

Relevant factors include:

• Advanced age – older patients often have reduced tissue elasticity, slower healing capacity, and increased vascular fragility, which may raise the risk of postoperative complications.
• Diabetes or impaired wound healing – diabetes can delay incision healing and increase susceptibility to infection.
• Hypertension – elevated blood pressure may increase the risk of postoperative bleeding or hematoma formation.
• Coagulation disorders or anticoagulation therapy – abnormalities in blood clotting or blood-thinning medications can increase bleeding risk during and after surgery.
• Previous radiation therapy – irradiated tissue may have reduced blood supply and impaired healing, making surgery technically more demanding.
• Prior cranial surgeries – previous operations can create scar tissue that obscures normal anatomy and increases the complexity of reoperation.
• Scar tissue from earlier trauma – fibrotic tissue may distort natural anatomical planes and increase surgical difficulty.
• Vascular fragility – weakened or diseased blood vessels are more prone to injury or bleeding during manipulation.
• Pre-existing neurological deficits – already compromised brain tissue may have limited reserve capacity, meaning even minor additional stress can produce noticeable symptoms.

These elements may increase susceptibility to infection, delayed healing, ischemia, or prolonged cerebral edema.

The same surgical maneuver may produce different outcomes depending on the resilience of the surrounding tissue.

3. Surgical Technique and Intraoperative Decisions

Technical aspects of the operation also contribute to risk.

These include:

• Degree and duration of brain retraction
• Handling of arteries, veins, and perforating vessels
• Extent of lesion removal
• Hemostasis technique
• Quality of dural closure
• Bone flap fixation
• Intraoperative blood loss

However, surgical technique is not static. An experienced neurosurgeon continuously adapts strategy according to tissue response, vascular anatomy, intraoperative findings, and neuromonitoring feedback.

The goal is always to balance adequate treatment of the pathological process with maximal preservation of neurological function.

4. Systemic Physiological Factors

Not all complications originate directly from local surgical manipulation.

Systemic factors may influence postoperative outcome, including:

• Intraoperative hypotension
• Oxygenation disturbances
• Blood pressure instability
• Cardiac events
• Fluid and electrolyte imbalance
• Coagulation abnormalities

For example, postoperative ischemia may reflect systemic blood pressure changes rather than direct arterial injury. Similarly, bleeding risk may increase in the presence of clotting disorders.

5. Progression of the Underlying Disease and Secondary Changes

Some complications develop after surgery due to evolving pathophysiological processes.

These may include:

• Delayed hematoma formation
• Progressive cerebral edema (often peaking 24–72 hours postoperatively)
• Changes in intracranial pressure
• CSF circulation disturbances
• Postoperative seizures
• Secondary infection

Not all adverse events are immediate. Some arise as part of the brain’s inflammatory and healing response following surgical intervention.

Multifactorial Nature of Complications

Complications are often not caused by a single mistake or isolated event, but by the combined effect of anatomical complexity, biological vulnerability, and necessary surgical intervention.

For example, a new neurological deficit after tumor removal may reflect:

• Tumor location in a functional brain area
• Necessary vascular manipulation
• Pre-existing tissue vulnerability
• Intraoperative hemodynamic changes
• Postoperative edema

Understanding these interactions is essential when evaluating whether a postoperative event represents an inherent surgical risk, disease-related progression, systemic physiological influence, or a potentially preventable technical complication.

Layer-by-Layer Complications After Craniotomy and Brain Surgery

Complications are best understood according to surgical layers:

1. Skin (scalp)
2. Bone (cranial flap)
3. Dura mater — the tough protective membrane beneath the skull
4. Brain tissue

They may be:

• Early (days to weeks)
• Late (weeks to months)
• Normal postoperative reactions
• Pathological complications

Skin Complications After Craniotomy

Early Expected Postoperative Findings

• Swelling – mild soft tissue edema around the incision is common during the first several days.
• Bruising – subcutaneous blood discoloration may extend beyond the incision due to gravity.
• Temporary numbness – small sensory scalp nerves are inevitably divided during incision, which may cause localized numbness around the scar. Sensation often partially improves over time, though a small area of reduced sensitivity may persist.
• Mild discomfort – localized incision-related pain is expected and typically improves gradually.

Early Pathological Complications

• Subgaleal hematoma – a collection of blood beneath the scalp (above the skull), presenting as a soft, sometimes tense swelling that may enlarge and cause pressure discomfort.
• Wound infection – increasing redness, warmth, tenderness, drainage, or fever beyond the normal inflammatory response.
• Wound separation (dehiscence) – partial or complete opening of the surgical incision.
• Skin necrosis (rare) – usually limited to the wound edges, appearing as darkened or blackened tissue at the margins due to impaired blood supply.

Late Complications

• Painful scar
• Hair loss along incision
• Delayed healing or persistent low-grade infection
• Temporalis muscle atrophy or dysfunction – thinning or weakness of the temporal muscle due to surgical dissection, retraction, or partial detachment. This may lead to visible hollowing of the temple region, jaw fatigue while chewing, or localized discomfort. In most cases, symptoms gradually improve, but mild contour asymmetry may persist.

Treatment and Prognosis

Most heal without long-term consequences.
Infections require antibiotics and sometimes surgical revision.

Bone (Cranial Flap) Complications After Craniotomy

During a craniotomy, a section of skull bone (the cranial flap) is temporarily removed and then fixed back in place. Although the bone is replaced at the end of surgery, healing of the bone and surrounding tissues may involve certain expected changes or, rarely, complications.

Early Expected Postoperative Findings

• Mild tenderness – local sensitivity over the surgical area is common during the first weeks and usually improves gradually.
• Temporary contour irregularity – slight unevenness or subtle asymmetry may be felt at the surgical site while swelling resolves and bone healing progresses.

These findings are generally part of normal recovery.

Early Pathological Complications

• Epidural hematoma – bleeding between the skull and the outer covering of the brain. It may cause increasing headache, neurological worsening, or reduced alertness and requires requires urgent evaluation if it is compressive.
• Bone flap displacement – rare shifting or instability of the replaced bone segment, sometimes associated with trauma or fixation failure.
• Acute inflammation/infection (osteitis) – early infection of the bone flap, usually presenting with increasing pain, swelling, redness, or wound drainage. This usually requires debridement (surgical cleaning of the infected tissue) along with the removal of the bone flap.

Late Complications

• Bone flap resorption – gradual thinning or weakening of the replaced bone, more common in younger patients or after large craniotomies.
• Chronic osteomyelitis – persistent bone infection that may develop months later, often associated with recurrent wound problems. Definitive treatment often involves surgical removal of infected bone and staged reconstruction.
• Cosmetic deformity – visible or palpable irregularity of the skull contour caused by uneven bone healing, partial bone flap resorption, a small bone defect left after removal of part of the skull, or a larger skull defect after decompressive craniectomy.

Treatment and Prognosis

Most bone-related issues resolve without long-term consequences.

When infection occurs, treatment may require antibiotics and, in more severe cases, temporary removal of the bone flap. A delayed reconstruction (cranioplasty) can later restore skull integrity and cosmetic appearance.

Early recognition and appropriate management are key to preventing more serious complications

Dura Mater Complications After Craniotomy

The dura mater is the protective membrane covering the brain. During craniotomy, it is opened and later carefully closed. Most dural healing proceeds without difficulty, but certain changes may occur.

Early Expected Postoperative Findings

• Headache related to dural tension – mild to moderate headache is common after surgery because the dura is richly innervated and sensitive to manipulation.
• Small sterile fluid collections – minor postoperative fluid beneath the scalp or dura may be seen on imaging and often resolves spontaneously.

These findings are usually temporary and improve over time.

Early Pathological Complications

• Cerebrospinal fluid (CSF) leak – leakage of clear, watery fluid from the wound or through the nose may indicate incomplete dural closure. Nasal leakage (CSF rhinorrhea) is most commonly associated with procedures involving the frontal or skull base sinuses. Accumulation of clear fluid beneath the scalp incision may suggest a localized CSF collection due to dural insufficiency, often referred to as a pseudomeningocele. Progressive swelling at the surgical site or increasing fluid collection warrants evaluation of CSF dynamics (forming hydrocephalus) and intracranial pressure. Persistent leakage increases the risk of infection, including meningitis.
• Subdural hematoma – bleeding beneath the dura that may cause headache, confusion, progressive neurological deficit, or decreased level of consciousness. Small, stable collections may be observed with imaging follow-up. However, if the hematoma becomes compressive and produces neurological deterioration, urgent surgical evacuation may be required.
• Meningitis – infection involving the protective coverings of the brain, typically associated with fever, neck stiffness, or altered consciousness.
• Tension pneumocephalus – accumulation of trapped intracranial air under pressure, which may cause worsening headache, confusion, decreased alertness, or new neurological deficits. In mild and stable cases, treatment may include close monitoring and high-flow oxygen therapy to accelerate air resorption. If seizures occur, anti-seizure medication may be administered. When intracranial pressure rises or neurological deterioration progresses, urgent intervention may be required, including needle aspiration, surgical decompression, or revision of the dural closure—particularly if a persistent communication with paranasal sinuses is suspected.

Late Complications

• Pseudomeningocele – a localized collection of cerebrospinal fluid under the scalp due to incomplete dural healing, often presenting as a soft fluctuating swelling.
• Chronic subdural collections – slow accumulation of fluid or blood beneath the dura over weeks to months.
• Adhesive headaches – persistent headache related to scarring and altered dural mobility.

Treatment and Prognosis

Most minor CSF leaks resolve with conservative measures such as observation, head elevation, or temporary lumbar drainage.

Persistent leaks may require surgical revision of the dural closure. Untreated leaks increase the risk of infection, including meningitis.

When identified early, most dural complications can be effectively managed.

Brain (Parenchymal) Complications After Craniotomy and Open Brain Surgery

Brain tissue complications are generally the most clinically significant because they directly affect neurological function.

Early Expected Postoperative Findings

• Temporary neurological worsening – This depends heavily on the location of the surgical target (e.g., tumor, hematoma, cyst) and proximity to vital brain centers. For instance, surgery in the temporal or frontal region in the dominant hemisphere may cause transient speech disturbances (aphasia); a frontoparietal approach carries a risk of mild weakness in the opposite half of the body, while occipital procedures may cause temporary visual changes. These deficits occur shortly after surgery due to tissue manipulation or localized swelling (edema) and typically resolve as the brain heals.
• Mild cerebral edema – localized brain swelling is common after surgery and often peaks within the first 24–72 hours.
• Fatigue – profound tiredness is common after major brain surgery.
• Slower cognition – temporary difficulty concentrating or processing information may occur during recovery.

These changes often improve gradually as swelling decreases.

Early Pathological Complications

Intracerebral hemorrhage – bleeding within the brain tissue that may cause sudden neurological deterioration. Small, stable hemorrhages are sometimes managed with close monitoring and repeat imaging, while larger or compressive hematomas may require urgent surgical evacuation and stabilization of intracranial pressure.

Significant brain swelling – excessive postoperative edema leading to increased intracranial pressure and worsening symptoms. Treatment typically involves close monitoring in an intensive care setting, medications that reduce brain swelling, careful control of blood pressure and oxygen levels, and in severe cases, additional surgical measures to relieve pressure.

Ischemic stroke – reduced blood flow to a region of the brain due to vascular compromise during or after surgery; management focuses on stabilizing circulation, supporting brain oxygen supply, and early rehabilitation, and outcome depends on the size and location of the affected area.

Seizures – abnormal electrical activity occurring in the early postoperative period.; usually treated with anti-seizure medication, which may be temporary in isolated events but sometimes requires longer-term therapy.

Late Complications

Persistent neurological deficit – weakness, speech disturbance, visual impairment, or sensory loss that does not fully resolve after the expected recovery period; management centers on structured rehabilitation and functional adaptation strategies. Each craniotomy carries specific neurological risks and potential deficits depending on its anatomical location.

Epilepsy – recurrent seizures developing months after surgery; typically managed with long-term anti-epileptic medication adjusted to seizure type and clinical response.

Hydrocephalus – disturbance of cerebrospinal fluid circulation leading to ventricular enlargement and progressive symptoms such as gait instability, cognitive decline, or headache; symptomatic cases may require cerebrospinal fluid diversion through temporary drainage or permanent shunt placement.

Cognitive or personality changes – lasting alterations in memory, executive function, emotional regulation, or behavior; treatment involves neuropsychological evaluation, cognitive rehabilitation, and supportive therapy.

Headache After Craniotomy: What Is Normal and What Is Not

Headache after craniotomy is common. It may appear in the early postoperative period or persist for months in some patients. In most cases, it represents a normal part of tissue healing. In a smaller number of cases, it may signal a complication that requires evaluation.

Why does headache occur after craniotomy?

Several mechanisms contribute:

• Scalp incision and division of small sensory nerves
• Opening and closure of the dura mater (which is richly innervated)
• Removal and fixation of the bone flap
• Muscle dissection, especially in temporal or suboccipital approaches
• Local inflammation and healing response
• Temporary changes in intracranial pressure dynamics

Early postoperative headache is usually expected and gradually improves over days to weeks.

When Do Headaches Occur and What Are the Symptoms?

In the early phase (first days to weeks), headache is often:

• Pressure-like or throbbing
• Localized around the incision
• Worse with coughing, bending, or straining
• Gradually improving as swelling decreases

Postoperative swelling typically peaks within 24–72 hours and then subsides.

When should headache raise concern?

Headache requires urgent medical evaluation if accompanied by:

• Repeated vomiting
• Progressive neurological worsening
• Increasing drowsiness
• Fever and wound redness
• Clear fluid leakage from the incision or nose
• New-onset seizures

In such situations, imaging is required to exclude complications such as hematoma, hydrocephalus, cerebrospinal fluid (CSF) leak, or infection.

Chronic Post-Craniotomy Headache

A subset of patients develops headache lasting more than three months. This is referred to as chronic post-craniotomy headache. Reported incidence varies but is generally estimated at approximately 15–30%, depending on surgical approach and definition used.

It is more common after:

• Retrosigmoid (retromastoid) craniotomy
• Lateral suboccipital approaches
• Skull base procedures
• Larger muscle dissections

Why is retromastoid headache relatively common?

In retrosigmoid or lateral suboccipital craniotomies, chronic headache may result from:

• Irritation or partial injury of occipital nerves
• Muscle scarring and tension
• Dural scarring
• Bone edge sensitivity
• Rarely, hardware-related irritation – metal plates or screws used to fix the bone may cause local irritation or tenderness. This is uncommon, and symptoms usually improve over time.

Pain is often localized to the occipital region and may radiate toward the top of the head or behind the eye. It can be triggered or worsened by neck movement and may resemble occipital neuralgia.

Management in these cases may include:

• Neuropathic pain medication
• Occipital nerve block
• Physical therapy
• Targeted pain management strategies

Most patients experience gradual improvement over time, although some may require structured pain management for conditions such as chronic headache or occipital neuralgia.

How is post-craniotomy headache treated?

Treatment depends on cause and duration.

In the early postoperative phase:

• Standard analgesics
• Careful monitoring
• Imaging if symptoms are atypical or worsening

In the chronic phase:

• Neuropathic pain medications
• Nerve blocks when indicated
• Physical therapy and muscle rehabilitation
• Individualized pain management strategies

Persistent or worsening headache should always be interpreted in the context of neurological examination and imaging findings.

Key Clinical Principle

Headache alone does not automatically indicate a complication. However, headache combined with neurological decline, fever, fluid leakage, or progressive symptoms requires urgent assessment to exclude bleeding, infection, hydrocephalus, or other postoperative complications.

Cognitive and Emotional Changes After Craniotomy and Brain Surgery

Cognitive and emotional changes are among the most common concerns after brain surgery. They do not automatically indicate a complication. In many cases, they reflect temporary brain swelling, tissue manipulation during surgery, metabolic stress, medication effects, sleep disruption, or the psychological impact of a serious diagnosis.

These changes are most often observed after surgery involving the frontal lobe (behavior, decision-making, motivation), temporal lobe (memory, language), dominant hemisphere speech areas, and deeper limbic structures. Even operations in other regions may indirectly affect cognition due to postoperative swelling or systemic stress.

Patients may notice slower thinking, reduced concentration, short-term memory difficulties, word-finding problems, mental fatigue, irritability, anxiety, or emotional sensitivity. Family members sometimes describe the patient as “less sharp,” more withdrawn, or emotionally reactive in the early recovery phase.

In most cases, cognitive slowing improves gradually as swelling resolves and the brain adapts. Recovery can continue for weeks or months depending on surgical location, lesion size, pre-existing brain condition, and overall health.

Persistent cognitive or personality changes are more likely when surgery involves functional cortical regions, when there was pre-operative neurological compromise, or when postoperative complications such as stroke, hydrocephalus, or significant edema occur.

Management focuses on structured recovery: adequate sleep, gradual return to activity, cognitive pacing (avoiding mental overload), medication review, and when necessary, formal neuropsychological assessment and cognitive rehabilitation. Emotional symptoms such as anxiety or depression are common after major brain surgery and are treatable with appropriate support.

Understanding that many of these changes are part of the brain’s healing process helps distinguish expected recovery from true complications. However, progressive worsening, new focal deficits, severe confusion, or decline in alertness require medical evaluation.

Normal Recovery vs Warning Signs

Not all postoperative symptoms indicate a complication. However, urgent medical evaluation is necessary if any of the following occur:

• Sudden or progressive neurological worsening
• Severe headache accompanied by repeated vomiting
• Fever combined with wound redness or drainage
• Clear fluid leaking from the incision
• New-onset seizures
• Increasing confusion or reduced alertness

Early assessment can prevent more serious consequences.

Second Opinion After Craniotomy

A second opinion may be reasonable when:

• Recovery is slower than expected
• Imaging findings are unclear or concerning
• A persistent neurological deficit remains unexplained
• Additional surgery is being proposed
• There is uncertainty about residual tumor or postoperative complications

Independent review of imaging studies, operative reports, and postoperative course can often clarify whether findings represent expected recovery, disease progression, or a true surgical complication.

Frequently Asked Questions About Craniotomy and Brain Surgery Complications

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