Common neurologic emergencies for nonneurologists: When minutes count

Management of subarachnoid hemorrhage

Early management of blood pressure for a ruptured intracranial aneurysm follows strategies similar to those for intracranial hemorrhage. Further investigation is rapidly directed toward an underlying vascular malformation, with intracranial vessel imaging such as CT angiography, magnetic resonance angiography, or the gold standard test—catheter-based cerebral angiography.

Aneurysms are treated (or “secured”) either by surgical clipping or by endovascular coiling. Endovascular coiling is preferable in cases in which both can be safely attempted.³¹ If the facility lacks the resources to do these procedures, the patient should be referred to a nearby tertiary care center.

INTRACRANIAL HYPERTENSION: DANGER OF BRAIN HERNIATION

A number of conditions can cause an acute intracranial pressure elevation. The danger of brain herniation requires that therapies be implemented rapidly to prevent catastrophic neurologic injury. In many situations, nonneurologists are the first responders and therefore should be familiar with basic intracranial pressure management.

Initial symptoms of acute rise in intracranial pressure

As intracranial pressure rises, pressure is typically equally distributed throughout the cranial vault, leading to dysfunction of the ascending reticular activating system, which clinically manifests as the inability to stay alert despite varying degrees of noxious stimulation. Progressive cranial neuropathies (often starting with pupillary abnormalities) and coma are often seen in this setting as the upper brainstem begins to be compressed.

Initial assessment and treatment of elevated intracranial pressure

Noncontrast CT of the head is often obtained immediately when acutely elevated intracranial pressure is suspected. If clinical examination and radiographic findings are consistent with intracranial hypertension, prompt measures can be started at the bedside.

Elevate the head of the bed to 30 degrees to promote venous drainage and reduce intracranial pressure. (In contrast, most other hemodynamically unstable patients are placed flat or in the Trendelenburg position.)

Intubation should be done quickly in cases of airway compromise, and hyperventilation should be started with a goal Paco₂ of 30 to 35 mm Hg. This hypocarbic strategy promotes cerebral vasoconstriction and a transient decrease in intracranial pressure.

Hyperosmolar therapy allows for transient intracranial volume decompression and is the mainstay of emergency medical treatment of intracranial hypertension. Mannitol is a hyper­osmolar polysaccharide that promotes osmotic diuresis and removes excessive cerebral water. In the acute setting, it can be given as an intravenous bolus of 1 to 2 g/kg through a peripheral intravenous line, followed by a bolus every 4 to 6 hours. Hypotension can occur after diuresis, and renal function should be closely monitored since frequent mannitol use can promote acute tubular necrosis. In patients who are anuric, the medication is typically not used.

Hypertonic saline (typically 3% sodium chloride, though different concentrations are available) is an alternative that helps draw interstitial fluid into the intravascular space, decreasing cerebral edema and maintaining hemodynamic stability. Relative contraindications include congestive heart failure or renal failure leading to pulmonary edema from volume overload. Hypertonic saline can be given as a bolus or a constant infusion. Some institutions have rapid access to 23.4% saline, which can be given as a 30-mL bolus but typically requires a central venous catheter for rapid infusion.

Comatose patients with radiographic findings of hydrocephalus, epidural or subdural hematoma, or mass effect with midline shift warrant prompt neurosurgical consultation for further surgical measures of intracranial pressure control and monitoring.

The ‘blown’ pupil

The physician should be concerned about elevated intracranial pressure if a patient has mydriasis, ie, an abnormally dilated (“blown”) pupil, which is a worrisome sign in the setting of true intracranial hypertension. However, many different processes can cause mydriasis and should be kept in mind when evaluating this finding (Table 3).³² If radiographic findings do not suggest elevated intracranial pressure, further workup into these other processes should be pursued.

STATUS EPILEPTICUS: SEIZURE CONTROL IS IMPORTANT

A continuous unremitting seizure lasting longer than 5 minutes or recurrent seizure activity in a patient who does not regain consciousness between seizures should be treated as status epilepticus. All seizure types carry the risk of progressing to status epilepticus, and responsiveness to antiepileptic drug therapy is inversely related to the duration of seizures. It is imperative that seizure activity be treated early and aggressively to prevent recalcitrant seizure activity, neuronal damage, and progression to status epilepticus.³³

Once the ABCs of emergency stabilization have been performed (ie, airway, breathing, circulation), antiepileptic drug therapy should start immediately using established algorithms (Figure 1).^34–36 During the course of treatment, the reliability of the neurologic examination may be limited due to medication effects or continued status epilepticus, making continuous video electroencephalographic monitoring often necessary to guide further therapy in patients who are not rapidly recovering.^34–38

Once status epilepticus has resolved, further investigation into the underlying cause should be pursued quickly, especially in patients without a previous diagnosis of epilepsy. Head CT with contrast or magnetic resonance imaging can be used to look for any structural abnormality that may explain seizures. Basic laboratory tests including toxicology screening can identify a common trigger such as hypoglycemia or stimulant use. Fever or other possible signs of meningitis should be investigated further with cerebrospinal fluid analysis.

SPINAL CORD INJURY

Acute spinal cord injury can lead to substantial long-term neurologic impairment and should be suspected in any patient presenting with focal motor loss, sensory loss, or both with sparing of the cranial nerves and mental status. Causes of injury include compression (traumatic or nontraumatic) and inflammatory and noninflammatory myelopathies.

The location of the injury can be inferred by analyzing the symptoms, which can point to the cord level and indicate whether the anterior or posterior of the cord is involved. Anterior cord injury tends to affect the descending corticospinal and pyramidal tracts, resulting in motor deficits and weakness. Posterior cord injury involves the dorsal columns, leading to deficits of vibration sensation and proprioception. High cervical cord injuries tend to involve varying degrees of quadriparesis, sensory loss, and sometimes respiratory compromise. A clinical history of bilateral lower-extremity weakness, a “band-like” sensory complaint around the lower chest or abdomen, or both, can suggest thoracic cord involvement. Symptoms isolated to one or both lower extremities along with lower back pain and bowel or bladder involvement may point to injury of the lumbosacral cord.

Basic management of spinal cord injury includes decompression of the bladder and initial protection against further injury with a stabilizing collar or brace.

Magnetic resonance imaging with and without contrast is the ideal study to evaluate injuries to the spinal cord itself. While CT is helpful in identifying bony disease of the spinal column (eg, evaluating traumatic fractures), it is not helpful in viewing intrinsic cord pathology.

Traumatic myelopathy

Traumatic spinal cord injury is usually suggested by the clinical history and confirmed with CT. In this setting, early consultation with a neurosurgeon is required to prevent permanent cord injury.

Guidelines suggest maintaining a mean arterial pressure greater than 85 to 90 mm Hg for the first 7 days after traumatic spinal cord injury, a particular problem in the setting of hemodynamic instability, which can accompany lesions above the midthoracic level.^39,40

Patients with vertebral body misalignment should be placed in an appropriate stabilizing collar or brace until a medically trained professional deems it appropriate to discontinue the device, or until surgical stabilization is performed.

Methylprednisone is a controversial intervention for acute spinal cord trauma, lacking clear benefit in meta-analyses.⁴¹

Nontraumatic compressive myelopathy

Patients with nontraumatic compressive myelopathy tend to present with varying degrees of back pain and worsening sensorimotor function. The differential diagnosis includes epidural abscesses, hematoma, metastatic neoplasm, and osteophyte compression (Table 4). The clinical history helps to guide therapy and should involve assessment for previous spinal column injury, immunocompromised state, travel history (which provides information on risks of exposure to a variety of diseases, including infections), and constitutional symptoms such as fever and weight loss.

Epidural abscess can have devastating results if missed. Red flags such as recent illness, intravenous drug use, focal back pain, fever, worsening numbness or weakness, and bowel or bladder incontinence should raise suspicion of this disorder. Emergency magnetic resonance imaging is required to diagnose this condition, and treatment involves urgent administration of antibiotics and consideration of surgical drainage.

Noncompressive myelopathies

There are numerous causes of noncompressive spinal cord injury (Table 4), and the etiology may be inflammatory (eg, “myelitis”) or noninflammatory. The diagnostic workup may require both magnetic resonance imaging and cerebrospinal fluid analysis. Acute disease-targeted therapy is rarely indicated and can be deferred until a full diagnostic workup has been completed.

NEUROMUSCULAR DISEASE: IS VENTILATION NEEDED?

Diseases involving the motor components of the peripheral nervous system (Table 5) share the common risk of causing ventilatory failure due to weakness of the diaphragm, intercostal muscles, and upper-airway muscles. Clinicians need to be aware of this risk and view these disorders as neurologic emergencies.

Determining when these patients require mechanical intubation is a challenge. Serial measurements of maximum inspiratory force and vital capacity are important and can be accomplished quickly at the bedside by a respiratory therapist. A maximum inspiratory force less than –30 cm H₂O or a vital capacity less than 20 mL/kg, or both, are worrisome markers that raise concern for impending ventilatory failure. Serial measurements can detect changes in these values that might indicate the need for elective intubation. In any patient presenting with weakness of the limbs, these measurements are an important step in the initial evaluation.

Myasthenic crisis

Myasthenia gravis is caused by autoantibodies directed against postsynaptic acetylcholine receptors. Patients demonstrate muscle weakness, usually in a proximal pattern, with fatigue, respiratory distress, nasal speech, ophthalmoparesis, and dysphagia. Exacerbations can occur as a response to recent infection, surgery, or medications such as neuromuscular blocking agents or aminoglycosides.

Myasthenic crisis, while uncommon, is a life-threatening emergency characterized by bulbar or respiratory failure secondary to muscle weakness. It can occur in patients already diagnosed with myasthenia gravis or may be the initial manifestation of the disease.^42–49 Intubation and mechanical ventilation are frequently required. Postoperative myasthenic patients in whom extubation has been delayed more than 24 hours should be considered in crisis.⁴⁵

The diagnosis of myasthenia gravis can be made by serum autoantibody testing, electromyography, and nerve conduction studies (with repetitive stimulation) or administration of edrophonium in patients with obvious ptosis.

The mainstay of therapy for myasthenic crisis is either intravenous immunoglobulin at a dose of 2 g/kg over 2 to 5 days or plasmapheresis (5–7 exchanges over 7–14 days). Corticosteroids are not recommended in myasthenic crisis in patients who are not intubated, as they can potentiate an initial worsening of crisis. Once the patient begins to show clinical improvement, outpatient pyridostigmine and immunosuppressive medications can be resumed at a low dose and titrated as tolerated.

Acute inflammatory demyelinating polyneuropathy (Guillain-Barré syndrome)

Acute inflammatory demyelinating polyneuropathy is an autoimmune disorder involving autoantibodies against axons or myelin in the peripheral nervous system.

This disease should be suspected in a patient who is developing worsening muscle weakness (usually with areflexia) over the course of days to weeks. Occasionally, a recent diarrheal or other systemic infectious trigger can be identified. Blood pressure instability and cardiac arrhythmia can also be seen due to autonomic nerve involvement. Although classically described as an “ascending paralysis,” other variants of this disease have distinct clinical presentations (eg, the descending paralysis, ataxia, areflexia, ophthalmoparesis of the Miller Fisher syndrome).

Acute inflammatory demyelinating polyneuropathy is diagnosed by electromyography and nerve conduction studies. A cerebrospinal fluid profile demonstrating elevated protein and few white blood cells is typical.

Treatment, as in myasthenic crisis, involves intravenous immunoglobulin or plasmapheresis. Corticosteroids are ineffective. Anticipation of ventilatory failure and expectant intubation is essential, given the progressive nature of the disorder.⁵⁰