Table 1 |.

TIAN grading scale

	Definition
Grade 1	Headaches associated with fevers OR mild worsening of existing neurological clinical signs and symptoms from baseline, resulting in minor functional deficits for which only observation or symptomatic management is needed
Grade 2	Moderate changes in the neurological exam from baseline that substantially affect function
Grade 3	Severe neurological clinical signs and symptoms that may affect critical cardiorespiratory functions OR clinical signs and symptoms of increased intracranial pressure (>20 mmHg) that are responsive to intervention*
Grade 4	Life-threatening, clinically significant elevated ICP (>20 mmHg) refractory to CSF drainage with no improvement in clinical symptoms in response to CSF drainage, possibly warranting urgent escalation of neurosurgical intervention (such as with emergent EVD or VPS placement)** OR concerning clinical signs and symptoms of impending/early herniation OR severe medullary dysfunction requiring endotracheal intubation for airway protection and/or mechanical ventilation

ICP (intracranial pressure), CSF (cerebrospinal fluid), EVD (external ventricular drain), VPS (ventriculoperitoneal shunt).

^*In patients with spinal cord tumors, grade 3 TIAN can occur when there is risk of debilitating loss of cord function.

^**Emergently accessing an existing device for CSF drainage does not necessarily qualify as grade 4 TIAN, if such drainage successfully manages ICP.