A common neurologic presentation in the emergency department (ED) is altered mental status. When a patient’s mental status is poor, the major concern is for an intracranial process causing brainstem dysfunction or elevated ICP and damage to the reticular activating system.

Describing the state of consciousness in words that qualify the degree of responsiveness is the first step of the assessment. Somnolence is a state where the patient can respond to voice; lethargy (and obtundation) is when they can respond to moderate (ie, repetitive tactile) stimuli, but quickly drift back to sleep; stupor is when they respond to vigorous repetitive stimuli (noxious stimuli); and coma is when there is absence of a response to any type of stimuli (unarousable unresponsiveness). Peripheral noxious stimuli (such as nail bed pressure) are used to elicit an eye-opening response and the central painful stimuli (such as trapezius twist, supraorbital pressure, and jaw margin pressure) are used to elicit a motor response.

The Glasgow Coma Scale (GCS) is a simple tool used to assess the degree of the obtundation; a single score is of limited value, underscoring the importance of regular, repeat assessments. It is a good prognostic test for patients with traumatic causes of altered mentation; it has less prognostic value in nontraumatic conditions, but provides a tool for monitoring responsiveness. The GCS includes eye-opening and verbal and motor response to different types of stimuli (we recommend pressure to the nail bed, followed by pressure to the supraorbital notch if needed); see Table 2.1. The maximum score is 15; 8 or less reflects a potential for cardiopulmonary compromise and the need for close monitoring.

Assessing cognition is rarely an emergency unless the change was recent. Screening for nonacute cognitive impairment using detailed assessment scales is not practical in the emergency setting, although especially in the elderly patient, it has an evolving role for proper disposition.

The main cognitive functions that are routinely assessed include orientation, memory, executive function, attention, and language. Orientation is classically tested by asking the patient to say the date and place; orientation to situation should be assessed as well by asking why they are in the hospital. Short-term memory can be evaluated by giving three words to memorize and prompting the patient about the words later during the encounter (delayed recall). Executive function can be assessed by asking the patient a series of questions (ie, “What number would you dial if there was a serious emergency?”), commands (ie, “Show me how you would make that call with this phone”), and to perform a series of motor tasks (ie, the three-step Luria test). Attention can be tested by asking the patient to repeat a sequence of numbers backward or spell a word backward.

Language has multiple parts including speech production, comprehension, naming, and repetition, and all of these should be assessed. Speech production can be involved in a lesion affecting the Broca area, which causes expressive (nonfluent) aphasia; the patient is, for the most part, able to follow commands and understand questions, but is unable to produce fluent speech. The patient’s
sentences are fragmented, nonfluent, and nonsensical, with paraphasias and grammatical errors. Receptive speech is when the lesion involves the Wernicke area and the patient is unable to understand commands and questions, and speech is usually fluent but not contextual. Repetition and naming should be assessed as well.

The patient’s capacity in making their own medical decisions should be assessed, especially in critical situations where their mental state could worsen and communication could be impaired. Testing for capacity can be done by any physician, and consists of determining whether a patient is able to understand the present situation, the benefits and risks of therapeutic options, and the consequences of the refusal of a treatment or procedure. They should be able to clearly state their wishes.

The Short Blessed Test (SBT), also called Orientation-Memory-Concentration Test, is a good screening test with a sensitivity of 95% with a cutoff value of >4 for abnormal. A score of 10 or more is consistent with dementia (Table 2.2).

CN I (olfactory nerve) passes through the cribriform plant and is often involved in lesions at the base of the skull (trauma, tumor, infection). Any involvement of the olfactory bulb or tracts can cause unilateral anosmia. The olfactory cortex receives input from both nerves, and unilateral involvement of the cortex rarely causes any anosmia.

To test this nerve, the patient must be conscious and able to cooperate. One should use subtle smells (ie, coffee) because noxious odors might be carried by the trigeminal nerve. The patient should have their eyes closed and each nostril tested separately.

CN II (optic nerve) forms at the retina initially; nasal fibers (temporal visual field) decussate at the optic chiasm and form optic tracts that give optic radiations traveling either to the lateral geniculate body and occipital cortex (vision) or superior colliculus and Edinger-Westphal nucleus (pupillary reflex); see Figure 2.1. Visual acuity, visual fields, color perception, and pupillary reflex should all be assessed.

Pupils should be inspected for size, symmetry, and reactivity to light. Asymmetry in pupillary size can be secondary to parasympathetic (CN III, Edinger-Westphal nucleus) involvement, causing the pupil to dilate (mydriasis), or sympathetic involvement, causing the pupil to constrict (myosis). Shape should also be assessed because abnormalities can be caused by ophthalmologic disorders (iris coloboma). Pupillary reflex (constriction) is triggered by light and accommodation, and is carried by the
optic nerve (afferent pathway) and returns to the circumferential pupillary sphincter by the parasympathetic fibers of the oculomotor nerve, CN III (efferent pathway, nerve fibers from Edinger-Westphal nucleus). Direct and indirect (to the contralateral eye) illumination causes constriction of both pupils (consensual reflex). The optic fibers that are responsible for this reflex pass ultimately to the ipsilateral and contralateral Edinger-Westphal nucleus (parasympathetic nucleus of the oculomotor nuclear complex), which projects axons to the ciliary ganglion (synapse) and then to the ciliary body (accommodation) and pupillary constrictors. Involvement of the optic nerve causes lack of response to light in the ipsilateral eye, but normal consensual response in both eyes when light is shone in the contralateral eye. Patients should be asked to fixate on a distant object to avoid myosis from accommodation. The afferent pupillary defect, or Marcus Gunn sign, is tested via the swinging flashlight test. When the light is on one eye, the pupils constrict initially and then dilate, and when the light moves to the affected eye, the initial constriction is lost, and the pupils continue to dilate. This sign most commonly signals the presence of an ipsilateral optic nerve lesion; it may also occur with homonymous visual loss related to optic tract lesions.