Pediatric emergency medicine trisk 111

period. Subtherapeutic antiepileptic drug levels are one of the most common
causes of seizures in this population. The presence of fever may indicate that a
febrile seizure has occurred or, if normal consciousness is not regained, that the
patient has contracted a CNS infection such as meningitis or encephalitis (see
Chapters 94 Infectious Disease Emergencies and 97 Neurologic Emergencies ).
The new onset of afebrile generalized seizures requires a more thorough
evaluation, as detailed in Chapter 72 Seizures .
Infection
Coma-inducing infections of the CNS may involve large areas of the brain and
surrounding structures, as in meningitis or encephalitis, or they may be confined
to a smaller region, as in the case of cerebral abscess or empyema (see Chapter 94
Infectious Disease Emergencies ). The incidence of bacterial meningitis due to
Haemophilus influenzae , Streptococcus pneumoniae and Neisseria meningitidis
has diminished among vaccinated children, but these infections still occur in
unvaccinated and undervaccinated patients, and in the immunocompromised.
Lyme disease is now present throughout the United States, and is a common
cause of meningitis. Meningitis may also be caused by viral (enteroviruses,
herpes), fungal (Candida, Cryptococcus ), mycobacterial (tuberculosis), and
parasitic (cysticercosis) organisms. These nonbacterial infections usually have a
slower onset of symptoms.
Encephalitis, or inflammation of brain parenchyma, may also involve the
meninges (see Chapter 94 Infectious Disease Emergencies ). It occurs most
commonly as a result of viral infection or immunologic mechanisms. Mumps and
measles were common causes before immunizations against these diseases, and
they still occur in unimmunized individuals or in individuals in whom immunity
has waned. Varicella encephalitis occurs 2 to 9 days after the onset of rash. The
incidence of arthropod-borne encephalitides varies by geographic location but
usually peaks in late summer and early fall. The herpes simplex virus (HSV)
remains the most common devastating cause of encephalitis, causing death or
permanent neurologic sequelae in the majority of patients. Beyond the neonatal
period, HSV affects the temporal lobes most severely, leading to seizures and

parenchymal swelling, which can cause uncal herniation.
Focal CNS infections include brain abscesses, subdural empyemas, and
epidural abscesses (see Chapter 94 Infectious Disease Emergencies ). Brain
abscesses occur most often in patients with chronic sinusitis, chronic ear
infection, dental infection, endocarditis, or uncorrected cyanotic congenital heart
disease. Subdural empyema also occurs as a result of chronic ear or sinus


infection, but it is most commonly seen as a sequela of bacterial meningitis.
Cranial epidural abscess is rare, but most cases occur from extension of sinusitis,
otitis, orbital cellulitis, or calvarial osteomyelitis.
Neoplasms
Alterations in consciousness as a result of intracranial neoplasms (see Chapter 98
Oncologic Emergencies ) may be caused by seizure, hemorrhage, increases in
ICP caused by interruption of CSF flow, or direct invasion of the brainstem by the
malignancy. The location of the tumor determines additional symptoms: Ataxia
and vomiting result from infratentorial lesions versus seizures, hemiparesis, and
speech or intellectual difficulties resulting from supratentorial ones.
Hydrocephalus caused by tumor growth most commonly presents with headache
(especially morning headache), decreased activity or lethargy, and vomiting.
Vascular
Coma of cerebrovascular origin is caused by interruption of cerebral blood flow
(stroke) as a result of hemorrhage, thrombosis, or embolism (see Chapter 97
Neurologic Emergencies ). Hemorrhage can be nontraumatic, stemming from
abnormal congenital vascular structures such as arteriovenous malformations
(AVM), aneurysms, or cavernous hemangiomas. Rupture of an AVM is the most
common cause of spontaneous intracranial bleeding among pediatric patients. The
hemorrhage is arterial in origin and located within the parenchyma, but it can
rupture into a ventricle or the subarachnoid space. Aneurysm rupture is less
common in children and is unusual in that repetitive episodes of bleeding may

occur (“sentinel bleeds”), with rising morbidity and mortality from subsequent
bleeding events. Subarachnoid blood may be present in either case, although
more commonly with aneurysm rupture. Cavernous and venous hemangiomas are
lower-flow lesions that produce less acute symptom onset.
Stroke may also occur from thrombosis or embolism of a normal vessel.
Cerebral infarction caused by occlusion of the anterior, middle, or posterior
cerebral artery usually produces focal neurologic deficit rather than coma. Acute
occlusion of the carotid artery, however, may produce sufficient unilateral
hemispheric swelling to cause herniation and coma. Cerebral sinovenous
thrombosis is most commonly seen with hypercoagulable states or as a sequela of
infections of the ear or sinus.
Swelling or hemorrhage from infarcted brain can cause increased ICP, leading
to decreased cerebral perfusion pressure and coma. Focal symptoms vary based
on the size and location of brain with inadequate blood supply. Vascular accidents


in the cerebellum present with combinations of ataxia, vertigo, nausea, occipital
headache, and resistance to neck flexion. Coma is an unusual early sign of
infarction of cerebral structures but becomes more common as lower anatomic
centers are affected. Occlusion of the basilar artery may result in upper brainstem
infarction, resulting in rapid onset of coma, as does hemorrhage or infarction of
the pons. Posterior reversible encephalopathy syndrome (PRES, a.k.a. reversible
posterior leukoencephalopathy syndrome [RPLS]) causing ALOC is associated
with autoimmune disease, sepsis, nephrotic syndrome, or immunosuppressive
agents.
Cerebrospinal Fluid Shunt Problems
Children with congenital or acquired hydrocephalus as a result of prematurityrelated hemorrhage, neoplasm, or trauma depend on the continued function of an
intraventricular shunt to drain CSF and maintain normal ICP (see Chapter 122
Neurosurgical Emergencies ). The most common shunt type is
ventriculoperitoneal (VP), draining CSF from a lateral cerebral ventricle through

a small skull burr hole and valve with an attached reservoir into the peritoneum
via subcutaneous tubing running through neck, chest, and abdomen. CSF shunts
may malfunction for many reasons, including shunt infection, tubing blockage,
rupture, disconnection, or valve malfunction. The risk of failure is greatest during
the first 6 months after shunt placement or revision.

Systemic Abnormalities
The second major category of disorders causing coma listed in Table 17.2 arise in
organs other than the CNS and affect the brain diffusely. These abnormalities
alter neuronal activity by a variety of mechanisms, including decreasing
metabolic substrates required for normal function (e.g., hypoxia, hypotension,
hypoglycemia, other electrolyte abnormalities), altering the rate of intracellular
chemical reactions (e.g., hypothermia, hyperthermia), and introducing extraneous
toxins into the CNS. Children with autoimmune disease such as systemic lupus
erythematosus, Behỗet disease, multiple sclerosis, and acute disseminated
encephalomyelitis (ADEM, a.k.a. postinfectious encephalitis) may present with
ALOC due to inflammation of brain parenchyma.
Hypoxia
Oxygen delivery to the brain may be adversely affected by disorders that
compromise a patient’s airway, breathing, or circulation. Neurons are the cells
most sensitive to oxygen deprivation, and they will cease to function within
seconds after being deprived of adequate levels of oxygen. Hypoxic coma may


result from airway obstruction, pulmonary disease, severe acute anemia, severe
methemoglobinemia, carbon monoxide poisoning, or asphyxia (e.g., drowning).
Permanent CNS dysfunction results from total anoxia lasting more than 4 to 5
minutes at normal body temperatures; lesser degrees of hypoxia may be tolerated
for longer periods. Submersion in near-freezing water may cool the brain
sufficiently to exert a neuroprotective effect, the magnitude of which is not

usually apparent in the emergency department. Hypercarbia may accompany
hypoxia and may contribute to neurologic depression and coma.
Cardiovascular Abnormalities
ALOC may be produced by poor cerebral perfusion resulting from insufficient
cardiac output or hypotension, as in hemorrhage, dehydration, septic shock,
dysrhythmia, and intoxication. Hypertensive encephalopathy is distinguished by
headache, nausea, vomiting, visual disturbance, ALOC, or coma in the presence
of a blood pressure greater than the 95th percentile for age and gender (see
Chapter 37 Hypertension ). The acute onset of severe hypertension may reflect
ongoing renal (e.g., unilateral renal artery stenosis, acute glomerulonephritis),
endocrine (e.g., pheochromocytoma), or cardiac (e.g., aortic coarctation)
pathology, or it may be the result of a toxic ingestion (e.g., cocaine).
Hypertension accompanied by bradycardia may be caused by increased ICP.
Disorders of Thermoregulation
Hypothermia or hyperthermia in the pediatric patient is usually caused by
prolonged environmental exposure to temperature extremes, such as those found
in cold water or in a closed car in sunlight (see Chapter 90 Environmental
Emergencies, Radiological Emergencies, Bites and Stings ). The child who
becomes comatose as a result of abnormal core temperature will have multiple
organ system abnormalities in addition to CNS dysfunction. Mental impairment is
progressive as body temperature is lowered, as each fall of 1°C produces a 6%
decline in cerebral blood flow. At 29° to 31°C, confusion or delirium is present,
as is muscular rigidity. Patients with core temperatures of 25° to 29°C are
comatose with absent deep tendon reflexes and fixed, dilated pupils. CNS
findings in hyperthermia include headache, vomiting, and obtundation, leading to
coma and/or seizures, especially above 41°C. Nonenvironmental causes of
hyperthermia include neuroleptic malignant syndrome, serotonin syndrome, and
malignant hyperthermia.
Toxic Ingestions