Emergency Craniotomy

Assess

Introduction

Consultation

History

Exam

On arrival to the Department of Emergency Medicine (DEM), the head trauma victim should be concomitantly resuscitated and evaluated for neurosurgical intervention. Surgical intervention is indicated primarily based on evaluation and analysis of data obtained from the neurologic physical exam and computerized tomography (CT) of the head. Once by CT and neuro exam it is determined that a patient requires surgery, formulation and execution of the surgical plan will require additional non-neurological physical exam and plain imaging (cervical spine) data.

Neurosurgical consultation

A neurosurgeon should be consulted for every patient brought into the emergency room with a head injury associated with a loss of consciousness of more than 1 minute or with a CT scan positive for: 1. Fracture, 2. Hemorrhage, or 3. Cerebral swelling. Patients with Glascow Coma Score of less than 15 with negative CT scans should be admitted to the hospital for observation.

In addition to clinical and tomographic data the surgeon must consider psychosocial and legal factors in the decision to perform a craniotomy on a particular head trauma victim. Laboratory and other imaging data is important as part of the preparation and planning of a surgery once it has been determined, on the basis of the criteria just mentioned, that surgical intervention is necessary.

Whether in the office or emergency department the surgeon formulates a differential diagnosis based on the patient's presentation: history and physical examination, prior to initiating a workup..

History

Historical information about the time and mechanism of a head injury can come from a variety of sources. Many patients are awake and alert when first seen by the paramedics at the site of injury. They can frequently describe the circumstances of a fall, assault, or vehicular collision. Patients unconsciousness "in the field" may be accompanied by witnesses to the injury who can give important information about the time of injury, length of unconsciousness, lucid interval, and occurrence of seizures, as well as past medical and medically significant social history.

The paramedic "run sheet" contains useful information about time and mechanism of injury as well as about abnormal breathing, pupillary size and reactivity, and presence of posturing. Witnesses interviewed by the paramedics may be unavailable by the time a patient arrives in the Emergency Department and the paramedic interview is frequently the only information of this kind available.

Family members can supply information about pre-injury medical condition and habits such as substance abuse that should figure into surgical planning. Family or friends may know if anisocoria was present before a head injury and can frequently provide a list of medications the patient was taking as well as the indication for each. There may have been an injury, mechanical or ischemic, resulting in a permanent neurologic deficit anteceding the current one.

The time from injury to assessment helps the surgeon assess the stage of evolution of the pathophysiology associated with an intracranial lesion. Most head injuries resulting in sustained (more than a few minutes) loss of consciousness are associated with a series of alterations in cerebrovascular, oncotic pressure, and electrolyte autoregulatory dynamics that result in ischemia, edema, and excitatory neurotransmitter toxicity. The findings of the neurologic and imaging examinations that determine patient candidacy for operation must be analyzed in the context of their temporal location in the pathophysiologic evolution.

An example of the importance of mechanism is that of a focal blunt force versus an acceleration-deceleration to the cranium. The former if delivered to the temporal petrous bone can result in fracture with laceration of the middle meningeal artery with resultant rapidly expanding epidural hematoma.

Rapid deceleration of the skull with continued movement of the brain can tear the small veins bridging the space between the pial surface and sagittal sinus resulting in a slowly expanding subdural hematoma associated with swelling of the underlying cerebral hemisphere and increased intracranial pressure evolving more slowly than the epidural due to laceration of the middle meningeal artery as it travels in its groove in the temporal bone. Even without a CT the surgeon should be suspicious of a rapidly expanding mass lesion (that may suddenly turn an awake into a comatose patient) with of a baseball bat to the side of the head, whereas the lethargy in a patient who fell from a second story window will more likely deepen progressively over the next few hours.

Paramedics can provide information about whether the patient was conscious or not at the time of their arrival on the scene, they may be able to comment on breathing pattern, and may have witnessed a seizure.

TIME OF INJURY
immediate hours  days chronic	primary secondary

The time of injury is an important factor because the management of primary and secondary injuries is different.

If the patient has been hypotensive

Physical examination

While historical information is important in predicting the pathophysiologic evolution and prognosis for neurologic recovery, information obtained from physical assessment of brain function is used, with imaging and social data, to determine not only if the patient requires neurosurgical intervention but also what kind of intervention and its optimal timing. The neurotrauma surgical indications physical exam includes not only an overall assessment of the level of brain function, but also for signs suggestive of irreversible coma as well as of impending or actual brain death.

Before performing the physical examination the surgeon should inquire about medications given by the paramedics in the field or after arrival at the DEM and should be aware of the effects of these agents on neurologic exam findings. Long-acting non-depolarizing paralytic medications such as pancuronium interfere with eye opening, motor responses, and verbalization necessary for determining a Glascow Coma Score. Both non-depolarizing and depolarizing agents (succinyl choline, for example) spare pupillary responses. Opiates or benzodiazepines used to sedate combative or uncooperative patients can significantly alter mental status but do not interfere with muscular contraction.

Glascow Coma Score

The GCS combines findings from three easily performed observer minimally dependent neurologic tests. Determination of the Glascow Coma Score has special significance because it is the current universally accepted measure of neurologic function and best predictor of outcome in head trauma victims. In the course of gathering information for determining the GCS the clinician will determine the patient's level of consciousness, detect the presence or absence of movement asymmetry suggestive of a focal deficit, and infer from the type of posturing, that there is ongoing diencephalic or brainstem dysfunction.

The GCS is the sum of three subscores of 1. eye opening, 2. extremity movement, and 3. verbal responses to graded intensity stimuli.

FIGURE Spontaneous and stimulated eye opening
Eye opening is graded 4 out of possible 4 if it is spontaneous, without any cutaneous or auditory stimulation. Three is the score for eye opening in response to an auditory stimulus. If noxious stimulation is required to elicit eye opening, the score is 2 out of 4. No eye opening to either auditory or painful cutaneous stimulation is graded 1.

Eye opening is impossible with paralytics on board and the surgeon should ask DEM personnel about possible prior administration of these before beginning his exam.

     Verbal response

FIGURE Intubated patient
Patients with severe head injuries who do not follow commands or are judged to be at risk for aspiration because of depressed airway protective reflexes are usually intubated early in the course of medical treatment. These patients cannot be assessed for a verbal response and their GCS subscore is recorded as "1 (intubated)". In patients who can respond verbally (patent airway, mobile vocal cords, intrinsic ventilatory mechanisms intact), the verbal score is 5 out of 5 for coherent, appropriate speech, 4 if the speech is fluent and comprehensible but confused, 3 if verbal output is not true speech but unintelligible words or phrases, 2 if only grunts, moans, or groans with no discernable words, and 1 if altogether absent.

     Motor response

Patients with severe head injuries who do not follow commands or are judged to be at risk for aspiration because of depressed airway protective reflexes are usually intubated early in the course of medical treatment. These patients cannot be assessed for a verbal response and their GCS subscore is recorded as "1 (intubated)". In patients who can respond verbally (patent airway, mobile vocal cords, intrinsic ventilatory mechanisms intact), the verbal score is 5 out of 5 for coherent, appropriate speech, 4 if the speech is fluent and comprehensible but confused, 3 if verbal output is not true speech but unintelligible words or phrases, 2 if only grunts, moans, or groans with no discernable words, and 1 if altogether absent.

The movements of the extremities elicited by varying degrees of stimulation are graded:

Protruding the tongue is another motor response that can used to test comprehension and ability to follow commands.

Comatose will often reflexively grasp a hand or fingers when these are placed in their palm and such squeezing following verbal or cutaneous stimulation does not indicate that the patient is following commands.

Pupillary responses

Fixed and dilated pupils are associated with shift of brain tissue and transtentorial herniation. The prognosis with or without surgical evacuation of a traumatic hematoma that causes herniation is poor. Bilateral fixed and dilated pupils are worse prognostically than a unilateral. The unilaterally fixed and dilated pupil is not necessarily on the same side as a surgical lesion but when head CT scanning is unavailable is on the side for the first three exploratory burr holes looking for epidural or subdural hematomas.

The afferent and efferent limbs of the pupillary response pathway should be kept in mind when assessing the light response in the presence of obvious ocular injury. Ophthalmologic consultation should be obtained in the event that enucleation is indicated immediately following craniotomy under the same general anesthesia.

Brainstem reflexes

Absent lower brainstem reflexes are frequently suggestive of irreversible coma that will likely progress to brain death.

Although it is obvious that brain dead patients are not candidates for craniotomy, such a travesty can occur if timely and accurate determination of irreversible absence of brain function is not done.

Papilledema results from decreased venous and possibly lymphatic outflow from the optic nerve head, which results in swelling seen with an ophthalmoscope as blurring of the optic disc margin in association with absence of retinal venous pulsations. Ophthalmoscopy is difficult in the brightly-lit DEM where the head-injured patient is initially evaluated. Pharmacologic pupillary dilation is of course absolutely contraindicated lest an essential element in neurologic assessment be compromised or impossible. Examination for papilledema is not necessary in the determination of a head trauma victim's eligibility for surgical intervention.

Although breathing patterns associated with lesions at different locations along the rostro-caudal neuroaxis are well-described, patients liable to Cheyne-Stokes, apneustic, ataxic breathing are all deeply comatose, intubated, and on mechanically controlled or assisted ventilation. Like papilledema, breathing pattern observed by paramedics in the field or prior to intubation is not important in determining whether or not a given patient requires surgical intervention.

TABLE Physical exam findings and significance