5.1 Neurological Assessment and GCS Motor Scales

Neurological Assessment and GCS Motor Scales

Introduction to Critical Care Neurological Assessment

In critical care transport medicine, a neurological assessment must be rapid, reproducible, and highly sensitive to subtle changes. When managing patients with acute neurological injuries in the transport environment, the clinician lacks immediate access to advanced diagnostic imaging like CT or MRI. Consequently, the physical examination serves as the primary diagnostic tool to identify impending brain herniation, guide airway management, and direct physiological resuscitation. Crucially, the transport neuro exam is not a static, one-time event; it is a continuous series of assessments where the trend in clinical status dictates life-saving interventions.

The Glasgow Coma Scale (GCS): Structure and Scoring

The Glasgow Coma Scale (GCS) remains the international standard for assessing consciousness and neurological impairment. Composed of three components—eye opening (E), verbal response (V), and motor response (M)—the scale ranges from a minimum score of 3 to a maximum of 15.

Eye Opening (E) Scoring

• 4 - Spontaneous: Eyes open without external stimulation.
• 3 - To Sound: Eyes open in response to verbal command or a loud shout.
• 2 - To Pressure: Eyes open only in response to a painful stimulus (e.g., nailbed pressure, trapezius squeeze).
• 1 - None: No eye-opening response to any stimulus.

Verbal Response (V) Scoring

• 5 - Oriented: Patient knows their name, current location, and the date/year.
• 4 - Confused: Patient speaks in coherent sentences but is disoriented to time, place, or person.
• 3 - Inappropriate Words: Patient utters random, recognizable words that do not form conversational sentences.
• 2 - Incomprehensible Sounds: Patient makes moaning or groaning sounds but no recognizable words.
• 1 - None: No verbalization or vocal output.
• T - Intubated: In patients who are intubated, the verbal score cannot be assessed and is documented as 'T' (e.g., GCS 5T or E2VtM3). This is a critical documentation point for exam purposes, as it indicates the patient has an advanced airway in place.

Motor Response (M) Scoring

The motor component is the most clinically significant and predictive of patient outcomes. It measures the integrity of the central nervous system from the cerebral cortex down to the brainstem.

• 6 - Obeys Commands: Patient performs simple actions on command (e.g., 'squeeze my hand', 'hold up two fingers'). Reflexive gripping (grasp reflex) is not obeying commands.
• 5 - Localizes to Pressure: In response to a painful stimulus (supraorbital notch pressure or trapezius squeeze), the patient moves their hand to or above the site of pain, crossing the midline or reaching above the clavicle.
• 4 - Normal Flexion (Withdrawal): The patient bends their elbow or pulls their limb away from the pain stimulus but does not localize, cross the midline, or raise the hand above the clavicle.
• 3 - Abnormal Flexion (Decorticate Posturing): The patient responds with adduction and internal rotation of the shoulder, flexion of the elbow, flexion of the wrist and fingers, and extension and internal rotation of the lower extremities. Decorticate posturing indicates severe dysfunction at or above the level of the red nucleus (midbrain), signifying injury to the corticospinal tract.
• 2 - Extension (Decerebrate Posturing): The patient responds with adduction and internal rotation of the shoulder, extension of the elbow, pronation of the forearm, flexion of the wrist and fingers, and extension of the legs with plantar flexion of the feet. Decerebrate posturing indicates a lesion below the red nucleus, involving the brainstem (midbrain or pons). This carries a significantly worse prognosis than decorticate posturing.
• 1 - None: No motor response to painful stimuli.

GCS-P (Glasgow Coma Scale with Pupillary Response)

Recognizing that pupillary reactivity is a vital indicator of brainstem function, the Brain Trauma Foundation and neurocritical care guidelines utilize the GCS-P. This scale subtracts the Pupillary Response Score (PRS) from the standard GCS score: GCS-P = GCS - PRS. The PRS is calculated based on the reactivity of the pupils to light:

• 2: Both pupils are unreactive to light (indicates bilateral brainstem/CN III compression).
• 1: One pupil is unreactive to light (indicates unilateral brainstem/CN III compression).
• 0: Both pupils are reactive to light.

A lower GCS-P score indicates more severe brain injury and correlates strongly with increased mortality.

Pupillary Assessment and Cranial Nerve Pathology

Pupillary evaluation is the window to the brainstem. The transport paramedic must assess pupillary size (in millimeters), symmetry, shape, and reactivity to light.

Anisocoria and CN III Compression

Anisocoria is defined as a pupillary asymmetry of greater than 1 mm. In the context of head trauma, a newly dilated, sluggish, or fixed pupil (mydriasis) is a neurosurgical emergency. This pathognomonic finding represents compression of Cranial Nerve III (Oculomotor Nerve) due to ipsilateral uncal herniation. As the uncus of the temporal lobe herniates through the tentorial notch, it compresses the outer parasympathetic fibers of CN III. Because these parasympathetic fibers are responsible for pupillary constriction, their dysfunction allows the sympathetic pathway to go unopposed, resulting in a dilated, fixed pupil on the ipsilateral (same) side as the lesion. Motor deficits (e.g., hemiparesis) will typically be contralateral (opposite) to the lesion due to decussation of the corticospinal tracts in the medulla.

Cranial Nerves Relevant to Flight Paramedicine

While a comprehensive cranial nerve exam is impractical in transport, key nerves must be assessed:

• CN II (Optic) and CN III (Oculomotor): Direct and consensual pupillary light reflexes.
• CN V (Trigeminal) and CN VII (Facial): Corneal reflex (used to assess brainstem function in comatose patients).
• CN IX (Glossopharyngeal) and CN X (Vagus): Gag and cough reflexes. A patient who lacks a gag or cough reflex cannot protect their airway, necessitating intubation.
• CN VIII (Vestibulocochlear): Evaluated via the oculocephalic reflex ('Doll's Eyes'). Turning the head side-to-side should result in eyes moving in the opposite direction of the turn. Fixed eyes in midposition indicate brainstem dysfunction. This assessment is strictly contraindicated in patients with suspected or un-cleared cervical spine injury.

Clinical Trends, Cushing's Triad, and Diagnostics

A single GCS assessment is merely a baseline. The transport paramedic must monitor for clinical trends. A decrease in the GCS score by 2 or more points, a new pupillary deficit, or a transition from localizing (M5) to posturing (M3/M2) indicates acute neurological decline.

Cushing's Triad is a classic, late sign of severe intracranial hypertension and impending brain herniation. It consists of:

1. Systolic Hypertension with a Widened Pulse Pressure: The brainstem becomes ischemic due to high ICP, triggering a massive sympathetic discharge to raise systemic blood pressure to maintain cerebral perfusion.
2. Bradycardia: The baroreceptors in the aortic arch and carotid sinuses detect the extreme hypertension and trigger a parasympathetic (vagal) response to slow the heart rate.
3. Irregular Respirations: Compression of the respiratory centers in the medulla oblongata leads to erratic breathing patterns (e.g., Cheyne-Stokes or Biot's respirations).

In spinal trauma, assess key dermatomes: C3-C5 (diaphragmatic pathway via the phrenic nerve; injury above C5 causes respiratory paralysis), T4 (nipple line), T10 (umbilicus), and S4-S5 (sacral sparing). Pathologic reflexes like the Babinski sign (great toe extension and fanning of other toes in response to plantar stimulation) indicate an upper motor neuron lesion.