Accommodation is the adaptation of eyes for near vision. It is demonstrated by having patient focus on object at arm’s length. When object is brought toward patient, the pupils should converge and constrict. This cannot be done on a comatose patient.

ALS, commonly known as Lou Gehrig’s disease, is a chronic progressive neurodegenerative disease of unknown cause that adversely affects the upper and lower motor neurons (wasting and weakness of muscles is related to lower motor damage, whereas spasticity and exaggerated weakness is related to upper motor neuron damage). Over time, motor neuron destruction leads to the inability to innervate and control voluntary muscle fibers. The result is muscle weakness and atrophy with eventual total loss of muscle function leading to respiratory failure and death. The disease does not affect the individual’s sensory or cognitive abilities.

Cerebral angiography is a diagnostic tool that produces images of the blood vessels of the brain with the added benefit of interventional capabilities during the procedure, if required. As with any angiogram, access is gained via the femoral or brachial arteries. A catheter is then threaded through this access to the carotid arteries, where contrast medium is injected directly into the arterial vasculature of the brain (known as “shooting the carotids”). Digital subtraction angiography (DSI) removes bone and tissue from the image, leaving only the dye-filled blood vessels for optimal visualization and interpretation. Postprocedure care includes observance of routine angiogram complications, as well as an added neurological assessment. Complications of this procedure include artery/arterial wall damage or dislodgement of debris such as plaque or a clot, which may result in a stroke.

Arteriovenous malformations (AVMs) are congenital brain lesions composed of tangled, dilated vessels that form an abnormal communication between arterial and venous systems. Intracranial “steal” occurs when the AVM is large, related to blood being diverted from one area of brain tissue because of lower vascularization in another area.

Signs and symptoms: Seizure activity is most common. Hemorrhage and/or headache occurs in about 50% of patients.

Treatment: Similar to aneurysms, though AVMs pose less risk of bleed with intervention.

Positive response for Babinski’s reflex is fanning of toes and extension of great toe with stimulation of plantar surface of foot. It is normal in babies but abnormal in adults. Response is related to upper motor neuron lesion and is seen on opposite side of cerebral damage.

Negative response is flexion of foot and is normal in adults.

Injury to the olfactory (first cranial) nerve is common with fracture, along with otorrhea or rhinorrhea. Drainage sample may be positive for glucose, though this is not always a reliable sign. Allow cerebrospinal fluid (CSF) to drain freely, keeping in mind that draining CSF due to a torn dura puts the patient at high risk for meningitis. Avoid NG, nasal suction, Valsalva’s maneuver, and cough. Raccoon eyes (ecchymotic areas around the eye orbits), epistaxis, visual defects, and anosmia are indicative of anterior fossa fracture, whereas Battle’s sign (ecchymosis over the mastoid bone 24 to 48 hours after injury), conductive hearing loss, and facial nerve palsy are indicative of posterior fossa fracture.

A processed EEG parameter used to measure the hypnotic effects of anesthetic and sedative agents on the brain. A sensor is placed on the patient’s forehead, and the BIS monitor translates information from the EEG into a single number (i.e., 100 = wide awake; 0 = absence of brain activity). Use of the BIS monitor does not replace the use of the peripheral nerve stimulator. Riker’s sedation-agitation scale is frequently used in conjunction with BIS monitoring to document the patient’s level of sedation.

Blood-brain barrier refers to the special permeability of brain capillaries and choroid plexus that limits transfer of certain substances into extracellular fluid of CSF of brain. H₂O, CO₂, O₂, and glucose cross easily. It is important because the blood-brain barrier is often damaged or infected when tissue is injured; damage leads to increased permeability.

Brain death diagnosis is made in the absence of hypothermia (temperature <32.2°C) and central nervous system depressants. Patient must be:

Brain stem collectively includes midbrain, pons, and medulla. It is an area that controls basic functions dealing largely with involuntary activities: blood pressure, heart rate, and respiration. Brain stem is “bottommost” in skull. Brain stem “trouble” can be identified by means of cranial nerve tests (see Cranial Nerve Exam).

Syndrome is due to incomplete lesion to one side of spinal cord, related to penetrating trauma. Assess for vibration sense, proprioception, and light touch.

In response to passive flexion of neck, hip and knees will flex. This is due to irritating exudate around roots in lumbar region. It is a sign indicative of meningitis or for bleeding into the subarachnoid space.

Designed to evaluate the eighth cranial nerve and the oculovestibular reflex in an awake patient, and the integrity of the brain stem on a comatose patient. It is considered to be one component in the evaluation of brain death, but is contraindicated in patients with cervical injury or a ruptured tympanic membrane. The patient is supine with the head of the bed up 30°. Instill 5 to 10 mL of water tympanically. Normal response depends on whether iced water or warm water is used, and whether patient is awake or unconscious.

Cerebral palsy is a disease resulting from brain damage in a newborn, and the exact cause is difficult to determine. At highest risk are the premature or babies who have a congenital malformation. Diagnosis usually involves a period of waiting (frequently up to 18 months) for the definite and permanent appearance of specific motor problems, that is, spasticity (inability of a muscle to relax) or athetosis (inability to control the movement of a muscle). Damage is fixed and rarely shows progression or regression. While there is no specific cure or standard therapy, drugs are often used for seizure and spasm control, and braces are used for muscle imbalance. Life expectancy varies with the severity of the disease.

Cerebral perfusion pressure (CPP) refers to the pressure difference across the brain between incoming mean arterial pressure (MAP) and the opposing intracranial pressure (ICP) (see table).

Cerebral salt wasting (CSW) is a syndrome of hyponatremia, natriuresis (excessive excretion of sodium in the urine), and a decrease in extracellular volume. Its existence as a diagnosis, and in some cases as a unique phenomenon, is greatly debated. While it closely resembles syndrome of inappropriate antidiuretic hormone (SIADH), there is one major differentiating factor. In SIADH, hyponatremia is a result of dilution. In CSW, hyponatremia is the result of primary sodium loss. However, a diagnosis of CSW can be made only if there is not excessive ADH in the body.

How exactly a neurologic insult leads to CSW is not yet clearly understood. It is thought that atrial natriuretic factors (ANF), substances released from the atria, play a part. ANF is also thought to cause diuresis, vasodilation, and suppression of the renin-aldosterone system.

CSW needs to be differentiated from SIADH because the treatments are the exact opposite of one another. In SIADH, the low sodium is treated with fluid restriction (to alleviate the dilutional state). In CSW, the treatment is to administer fluids (oral and hypertonic [3%] or isotonic IVs). This will replace the sodium that has already been excreted. The repletion should not be done faster than 0.7 mEq/L/hr for a maximum total daily change not to exceed 20 mEq/L. Fludrocortisone, a mineralocorticoid drug, is an adjunct to sodium and fluid replacement for CSW. It enhances sodium reabsorption in the renal tubules, allowing the body to retain more sodium.

CSF is made in lateral ventricles by choroid plexus. It is constantly produced and constantly absorbed. It circulates from ventricles in brain, around subarachnoid space and spinal cord. It is absorbed through villi into dura mater. Approximately 400 to 500 mL of CSF is made daily, or about 20 mL/hr. About 15 to 25 mL is located in each ventricle. It is characteristically clear and colorless (xanthochromic CSF is a sign of bleeding in area), with pressure of 80 to 180 mm H₂O while patient is side lying.

Abnormal lab values for CSF (the following are “rules of thumb” only):

These are a group of abnormalities of the craniocervical junction characterized by the hindbrain descending down through the foramen magnum. The malformation is divided into three types (see figure on the next page).

The abnormality is rare, affecting only 1 in 10,000 to 15,000, with males more commonly affected than females. Average age for diagnosis is estimated at 30 to 40 years for adults and 11 years for children. There is a wide variance in how these patients present clinically, probably accounting for frequent delays in diagnosis. Treatment generally requires surgical intervention consisting of either (1) local decompression or (2) diversion. Local decompression consists of removing the base of the back of the skull and the posterior portions of the uppermost vertebrae. This will widen the opening of the foramen magnum. Once the bone has been removed, the membrane (dura) overlying the cerebellum and spinal cord is opened. A tissue graft is then “spliced” into the dura to provide even more room for the easy passage of CSF. Less often, diversion is used, by draining the cavity within the spinal cord with a diverting shunt tube. This can be directed from the spinal cord cavity to either the chest or the abdominal wall.

The choroid plexus is a special capillary bed located in the brain that filters blood and is responsible for the production of cerebral spinal fluid.

Chvostek’s sign is a twitch of facial muscles, upper lip, and eye following a sharp tap to facial nerve (seventh cranial nerve) anterior to the ear, just below the temple. It is related to a decreased serum calcium level.

The circle of Willis is an anatomic juncture representing an anastomosis of four major vessels: posterior cerebral, anterior cerebral, internal carotid, and posterior/
anterior communicating. The “circle” is the most common site for an intracranial aneurysm.

Coma is a state defined as being unconscious, unarousable, and unresponsive to touch or sound. Coma is caused by one of two things:

The caloric test differentiates between the two (see Caloric Test).

A normal reflex, the consensual reflex is demonstrated by constriction of opposite pupil when light stimulates one eye.

The corneal reflex tests the fifth cranial nerve, the trigeminal. Touch cornea with wisp of cotton or place a drop of artificial tears in eyes and observe for blink reflex, or apply pressure
to supraorbital ridge and observe for facial grimacing (reflex is decreased or absent on same side as hemiplegia).

The 12 pairs of symmetrically arranged cranial nerves are attached to the brain and exit through a foramen at its base. The site where the fibers composing the nerve enter or leave the brain surface is usually termed the superficial origin of the nerve; the more deeply placed group of cells from which the fibers arise or around which they terminate is called the nucleus of origin.

To remember the names of the 12 nerves, remember the mnemonic “On old Olympian towering tops, a Finn and German viewed some hops.” But because the names of so many of the nerves begin with the same letter, also remember the mnemonic “Little people can only imitate big champions.” This gives the second letter (or third, if both second letters are the same) of the nerve. To remember the type of nerve, remember the mnemonic “Some say marry money, but my brother says (it is) bad business marrying money” (s = sensory; m = motor; b = both sensory and motor).

Creutzfeldt-Jakob disease (CJD) is a degenerative neurologic disease that is rapid and fatal, similar to “mad cow” disease (bovine spongiform encephalopathy, or BSE). Though the two are similar, no correlation of a relationship between them is evident. The onset of CJD manifests itself as confusion and then it progresses rapidly to coma and death, usually within 2 years, often within 1 year. The disorder is seen in adults with an average age of 60 years. Because it is infectious, standard precautions should be taken with invasive procedures or contaminated body fluids, especially spinal fluid or brain tissue.

When CSF pressure and the pressure within the intracranial cerebral arteries start to equilibrate, the cerebral arteries become compressed and begin to collapse. This compromises cerebral blood flow. Cushing’s reflex is activated, and the arterial pressure rises to a level higher than the CSF pressure, allowing cerebral blood flow to be reestablished and ischemia to be relieved. The blood pressure is maintained at a new, higher level, and the brain is protected from further loss of adequate blood flow. Cushing’s reflex causes the symptoms of Cushing’s triad.

The triad refers to three signs caused by Cushing’s reflex:

It is indicative of an advanced increase in intracranial pressure, that is, the brain’s “last gasp.” The triad and the reflex are late findings, and irreversible neurologic damage may have already occurred by the time they are recognized.

Decerebration is demonstrated by extension of involved extremities with outward pronation of the wrists and hands. Legs are stiffly extended at the knees with the feet plantar flexed. This indicates disruption of motor fibers in the midbrain and brain stem and is a more ominous sign than decortication.

Decortication is demonstrated by flexion of the upper extremities and extension and internal rotation of the lower extremities on the side of the lesion. It is seen in patients with interruption of cortical nerve fibers but intact pathways through the brain stem.

Also known as the oculocephalic reflex/response, Doll’s eyes testing is used on a comatose patient to check for an intact brain stem. It should never be performed on a suspected neck injury.

With eyelids held open, briskly turn the head either horizontally side-to-side (cranial nerves III, VI) or vertically up and down (cranial nerve III only).

Reflex normal (positive doll’s eyes, brain stem intact): Eyes move in the opposite direction of the head turn and then slowly drift back to the midline as if to fixate on a stationary object.

Ask the patient to close eyes and extend arms up with palms facing inward (“catch the rain” or “deliver a pizza”). Have patient count backward from 10 while maintaining elevated arms. Downward drift of one or both arms or pronation of palms indicates a positive drift and is indicative of mild hemiparesis.

Dysreflexia is a state unique to spinal cord injured patients at T5 and above, sometimes seen in patients with injury at T6 to T10. The cascade of events is triggered when an irritating stimulus (such as an overfilled bladder) is introduced to the body below the level of the injury. Since the impulse cannot reach the brain due to the injury, the body responds by initiating a reflex to increase the sympathetic portion of the autonomic nervous system. This results in spasms, narrowing of the blood vessels, and a rise in blood pressure. Nerve receptors in the heart and blood vessels detect this rise, and in an effort to control it, the brain sends a message to the heart causing the heartbeat to slow down and the blood vessels above the level of the injury to dilate. However, since the brain cannot deliver the same message to the receptors below the level of the injury, the blood pressure is unable to be regulated, and life-threatening hypertension ensues. Other common symptoms include headache, flushing, red blotches on skin above the level of the injury, and sweating above the level of the injury, due to vasodilation. Cold, clammy skin and goose bumps below the level of the injury are due to vasoconstriction. Nausea, as well as a metallic taste in the mouth, are due to vagal parasympathetic stimulation. Treatment must be initiated promptly and is aimed primarily at alleviating the precipitating stimulus, though often antihypertensives must be prescribed.