I Conditions arising from head trauma or primary central nervous system disease A Trauma Intracranial hematoma (subdural, epidural, subarachnoid) Cerebral contusion Diffuse cerebral edema Concussion B Seizures Status epilepticus (convulsive, nonconvulsive) Postictal state C Infection Meningitis Encephalitis Focal infections (brain abscess, subdural empyema, epidural abscess) D Neoplasms Tumor (edema, hemorrhage, blockage of CSF flow) E Vascular disease Cerebral infarct (thrombotic, hemorrhagic, embolic) Cerebral sinovenous thrombosis Subarachnoid hemorrhage Vascular malformation/aneurysm F Hydrocephalus Obstructive (from tumor or other cause) Cerebrospinal fluid shunt malfunction II Conditions affecting the brain diffusely A Vital sign abnormalities Hypotension, hypertension Hypothermia, hyperthermia B Hypoxia Pulmonary disease Severe anemia Methemoglobinemia Carbon monoxide Posthypoxic encephalopathy C Intoxications Sedative drugs: antihistamines, barbiturates, benzodiazepines, ethanol, gamma-hydroxybutyrate (GHB) and analogs, narcotics, phenothiazines, clonidine Tricyclic and other antidepressants Antipsychotics (i.e., risperidone, quetiapine, olanzapine)