The neurological exam

The neurological exam is a set of bedside tests, each built to check one part of the nervous system, so that a clinician can work out where a problem is before any scan is taken. This page goes through the components of the neurological exam in the usual order (mental status, cranial nerves, sensory, motor with reflexes, and coordination and gait), shows how the Glasgow Coma Scale scores consciousness, how to recognize a stroke, what a spinal cord injury does at each level, and how the findings are put together to place a lesion.

What the exam is for

A woman arrives with a weak right hand. The weakness could come from her left cerebral cortex, her internal capsule, her brainstem, her cervical spinal cord, a C8 nerve root, her ulnar nerve or the hand muscles themselves. Each of those places leaves a different pattern of findings, and the exam is designed to read the pattern.

The neurological exam is that structured set of tests. It asks two questions, in this order:

1. Where is the problem? This is localization. The exam answers it, using what you have learned about pathways: which side they serve, where they cross and which segment or nerve they use.
2. What is the problem? The history answers it, mostly from the time course: seconds (loss of blood flow), hours to days (infection, inflammation), months (a slowly growing mass or a degenerative disease).

The exam has five parts, and each one tests particular regions of the nervous system (Figure 1):

• the mental status exam tests the cerebrum;
• the cranial nerve exam tests the brainstem and its nerves;
• the sensory exam tests the ascending pathways, from nerve endings to the cortex;
• the motor exam, which includes the reflexes, tests the descending pathways, the lower motor neurons and the muscles;
• the coordination exam, with the gait exam, tests the cerebellum and the systems that feed it.

A full exam takes a long time. A screening exam checks a few items from each part in a few minutes, and the clinician goes into detail wherever something is abnormal.

The mental status exam

The mental status exam tests the cerebrum and the systems that keep you awake. It runs from the most basic function to the most complex:

• Level of consciousness. Alert, drowsy but rousable by voice, rousable only by pressure, or unresponsive. Staying awake depends on the reticular activating system of the brainstem acting on both hemispheres, so a drop in consciousness means either brainstem trouble or trouble affecting both hemispheres at once.
• Orientation. Does the person know who they are, where they are, the date and why they are here? A person who knows all four is "oriented times four".
• Attention. Can they repeat a string of digits, or count back from 100 by sevens?
• Memory. Can they recall three words after five minutes? That tests forming new long-term memories, which needs the hippocampus.
• Language. Fluency, comprehension, naming objects and repeating a sentence. You met the patterns in cortical functions: effortful, halting speech with good comprehension points to Broca's area (expressive aphasia); fluent speech with poor comprehension points to Wernicke's area (receptive aphasia). In most people both lie in the left hemisphere.
• Judgment and planning. Tested with a problem or a hypothetical situation. These executive functions depend on the prefrontal cortex.

The Glasgow Coma Scale

When a person is too unwell for a full mental status exam, for example after a head injury, their level of consciousness is scored with the Glasgow Coma Scale (GCS). It rates the best response in three categories and adds the scores:

The total runs from 3 (no response at all) to 15 (fully awake and oriented). Totals are grouped as mild (13 to 15), moderate (9 to 12) and severe (8 or less). A score of 8 or less is the usual working definition of coma. Clinicians report the parts as well as the total, because the same total can hide very different patients.

The cranial nerve exam

You met every cranial nerve test in the cranial nerves topic. In the exam they are run in number order, and each finding is compared across the two sides:

One test has its own name. The corneal reflex is the blink test: a wisp of cotton touched to the clear front surface of the eye makes both eyes blink. The touch travels in on the ophthalmic branch of the trigeminal nerve (V), crosses in the pons, and the blink goes out on both facial nerves (VII). It is a reflex arc through the brainstem, which is why it is also checked in a person who cannot cooperate: once sedating drugs and a very low body temperature are ruled out, an absent corneal reflex in a deeply unresponsive patient points to failure of the brainstem around the pons.

Cranial nerve findings are powerful for localization because each nerve joins the brainstem at a known level. A cranial nerve problem on one side together with weakness of the opposite side of the body points to the brainstem, as you will see below.

The sensory exam

The sensory exam tests each ascending pathway separately, because the two main pathways cross at different levels:

• Spinothalamic tract: pain, tested with a clean pin (pinprick), and temperature, tested with a cool metal object.
• Dorsal column pathway: vibration, tested with a buzzing tuning fork on a bony point such as the big toe joint, and joint position sense (proprioception): with eyes closed, is the toe being moved up or down?
• Light touch travels in both, so it is a general screen.

Each modality is tested on both sides and from the feet upward. Comparing the findings with the dermatomes tells you whether the loss follows one nerve root, one peripheral nerve, a "stocking" pattern in both feet (typical of disease of many peripheral nerves) or a sensory level, a line across the trunk below which sensation is lost, which means the spinal cord is damaged at about that segment.

Cortical sensation

If the basic sensations are intact, the clinician can test the parietal cortex, which turns raw touch into meaning. With eyes closed:

• Stereognosis (stereo- = solid, gnosis = knowledge): name an object, such as a coin or a key, placed in the hand.
• Graphesthesia (graph- = write, esthesia = sensation): name a number traced on the palm with a fingertip.
• Two-point discrimination: tell whether one point or two are touching the fingertip.

Failing these tests with normal pinprick, vibration and position sense points to the parietal lobe on the opposite side. If the basic sensations are already lost, these tests cannot be interpreted, because the information never reached the cortex.

The motor exam

The motor exam applies what you learned about upper and lower motor neurons. It has five parts:

1. Inspection. Muscle bulk (wasting), fasciculations and abnormal movements such as a tremor.
2. Tone. The clinician moves the relaxed limb: normal, reduced (flaccidity) or increased (spasticity, or the rigidity of Parkinson's disease).
3. Strength. Each muscle group is graded on a scale of 0 to 5.
4. Pronator drift. A sensitive test for mild upper motor neuron weakness in the arm.
5. Reflexes. Deep tendon reflexes graded 0 to 4+, and the plantar reflex.

For pronator drift, the person holds both arms straight out in front, palms up, and closes their eyes. A healthy person holds the position. With mild upper motor neuron weakness, one forearm slowly turns palm-down (pronates) and the arm drifts downward. It works because upper motor neuron damage weakens the supinators and extensors of the arm more than the pronators and flexors, and closing the eyes removes the visual correction.

The findings are then sorted with the table you met in motor pathways: weakness with raised tone, brisk reflexes and a Babinski sign points to the upper motor neuron; weakness with wasting, fasciculations, low tone and lost reflexes points to the lower motor neuron.

The coordination and gait exam

The coordination exam tests the cerebellum, in a person strong enough to move normally:

• Finger-to-nose: touch your nose, then the examiner's moving finger, back and forth. Overshooting (dysmetria) and a tremor that grows near the target point to the cerebellar hemisphere on the same side.
• Heel-to-shin: lying down, run one heel down the other shin, the same test for the leg.
• Rapid alternating movements: slap the thigh with the palm, then the back of the hand, as fast as you can. Clumsy, irregular rhythm is another cerebellar sign.

The gait exam watches the person walk normally, then heel-to-toe along a line (tandem walking), then on the heels and on the toes. Each abnormal gait points somewhere: a wide-based, staggering gait (ataxia) to the cerebellum, especially the vermis; a stiff leg swung out in an arc to upper motor neuron damage on that side; small shuffling steps to Parkinson's disease; a foot that slaps down or catches its toe to weakness of the muscles that lift the foot.

The Romberg test

Balance while standing uses three inputs: vision, the balance organs deep in the skull, and position sense from the legs, carried by the dorsal columns. In the Romberg test, the person stands with feet together, first with eyes open, then with eyes closed.

• Steady with eyes open, sways or falls with eyes closed: the test is positive. Position sense from the legs is lost, and vision had been making up for it. This points to the dorsal columns or the large sensory axons of the peripheral nerves.
• Unsteady even with eyes open: vision cannot make up for the problem. This is typical of cerebellar damage, and the Romberg test is not "positive" in the strict sense.

Recognizing a stroke

A man at a restaurant suddenly cannot hold his fork in his right hand. The right corner of his mouth droops, and when he tries to speak, the words come out wrong. Nothing hurt. This is what a stroke looks like.

A stroke, or cerebrovascular accident (CVA), is the sudden loss of function in part of the brain when its blood supply is interrupted. Neurons have almost no energy stores, so within minutes of losing blood flow they stop working, and they start to die soon after. A typical large ischemic stroke kills nearly two million neurons a minute, which is why the rule is "time is brain". There are two kinds:

Because the treatments are opposite, a brain scan must tell the two apart before any clot-dissolving drug is given. The signs alone cannot.

The warning signs

The public is taught the signs as BE FAST:

• Balance: sudden loss of balance or coordination.
• Eyes: sudden loss of vision in one or both eyes, or double vision.
• Face: one side of the face droops; ask the person to smile.
• Arm: one arm is weak; ask them to raise both arms and watch for one drifting down.
• Speech: slurred, strange or absent speech.
• Time: note when the person was last known to be well, and call emergency services at once.

The signs localize like any other finding. The restaurant patient has weakness of the right hand and lower right face, with sparing of the forehead, plus an aphasia. That places the damage in the left hemisphere, in the motor cortex for the face and hand and in the language areas next to it: one artery supplies that whole region.

Transient ischemic attack

A transient ischemic attack (TIA) is a brief episode of stroke-like signs caused by a temporary loss of blood flow, with no dead brain tissue on a scan. The signs usually last minutes, and most clear within an hour. A TIA is a warning: the risk of a full stroke is highest in the next few days, so it is treated as an emergency even though the signs have gone.

Spinal cord injury

A spinal cord injury cuts some or all of the tracts at one level and destroys the gray matter of the segments at that level. Below it, the cord's own circuits survive but lose their connection to the brain. Everything depends on the level:

• The neurological level is the lowest segment with normal sensation and strength on both sides.
• A complete injury leaves no movement or sensation at all in the lowest sacral segments. An incomplete injury spares some, and the chance of recovery is much better.

The diaphragm is the key to cervical injuries. Its phrenic nerves come from C3, C4 and C5, and students remember this as "C3, 4 and 5 keep the diaphragm alive". An injury above C3 stops breathing at once.

Right after a sudden injury, the cord below it goes quiet for days to weeks: the limbs are floppy and the reflexes absent. Then reflexes return and become brisk, with spasticity and Babinski signs, the upper motor neuron picture you met in motor pathways. At the level of the injury itself, the destroyed ventral horn cells leave a narrow band of lower motor neuron weakness.

Hemisection: damage to one half of the cord

You worked this pattern out in the sensory and motor pathways topics. When one half of the cord is cut, a hemisection (hemi- = half), also called Brown-Séquard syndrome, the tracts that have already crossed and those that have not yet crossed are both lost:

• Same side, below the injury: upper motor neuron weakness (the lateral corticospinal tract crossed in the medulla) and loss of vibration and position sense (the dorsal columns cross in the medulla).
• Opposite side, from a segment or two below: loss of pain and temperature (the spinothalamic tract crossed on entry).

Putting it together: localizing a lesion

Localization follows a fixed order of questions. Figure 2 shows the main branches.