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11 Neurologic Complications in Medical Patients

Karl E. Misulis, MD, PhD and E. Lee Murray, MD

OVERVIEW

This chapter presents a review of some of the most important neurologic complications seen in hospitalized patients. An issue of Continuum was devoted to this topic.¹

INFECTIONS

Systemic infections predispose to neurologic complications by metabolic, ischemic, and direct inflammatory effects. Most patients with neurologic complications have sepsis or systemic inflammatory response syndrome (SIRS).

Sepsis and SIRS

SIRS is usually but not invariably due to infection, other causes being ischemia, trauma, burns, and inflammation due to autoimmune and other reasons. SIRS is defined as having at least two of the following²:

Sepsis is defined as at least two SIRS criteria, and the cause is known or suspected infection.

Severe sepsis is defined as sepsis with acute organ dysfunction caused by the sepsis, usually from hypotension and hypoperfusion. Organ dysfunctions can include altered mental status.

Septic shock is defined as sepsis with persistent or refractory hypotension or tissue hypoperfusion despite adequate fluid resuscitation.

Multiorgan dysfunction syndrome (MODS) is defined as the presence of organ dysfunction in an acutely ill patient such that homeostasis cannot be maintained without intervention.

Neurologic complications are most prominent with increasing severity of the sepsis.

Encephalopathy

Encephalopathy is the most common neurologic complication of systemic infections and SIRS. Mild confusion from urinary tract infections (UTIs) or other infections is often overlooked initially.

PRESENTATION of the encephalopathy can begin with delirium, with difficulties with attention, disorientation, and confusion. Lethargy may develop, especially with metabolic derangements from the underlying condition. The disorder may progress to coma.

DIAGNOSIS is clinical, but the specific label of septic encephalopathy is given when other diagnoses have been eliminated.

Differential Diagnosis

Differential diagnoses to consider include:

Studies which should be considered include:

Nonconvulsive seizure in critically ill patients is underdiagnosed. Patients with nonconvulsive seizures are usually lethargic or minimally responsive.

Meningitis can be missed or diagnosed late. Although hospital-acquired bacterial meningitis is uncommon in a patient who has not had CNS instrumentation, a patient admitted with presumed pneumonia or other systemic infection with mild delirium may ultimately be found to have meningitis.

Encephalitis may present with nonspecific symptoms initially, and, if the patient is found in the ED to have a UTI or other systemic infectious source, diagnosis of encephalitis may be delayed until more dramatic neurologic findings develop, such as marked encephalopathy, seizures, or focal signs.

Lumbar epidural abscess can rarely present with encephalopathy with systemic signs of infection.³ MRI of the spine may be indicated, especially if there is a history of spine pain or if the patient has limb weakness in a distribution suggesting a cord lesion.

Seizures

Seizures in the ICU can be convulsive or nonconvulsive. Seizures in a patient with SIRS or sepsis can be due to CNS infection or vascular disease. Also, some antibiotics, such as cefepime and meropenem,⁴ predispose to seizures. Renal insufficiency increases the risk of medication-induced seizures, as does renal failure itself.

PRESENTATION of seizures in the ICU can be generalized motor, focal motor, multifocal motor, or subtle. Patients with marked unresponsiveness without an obvious cause on labs and imaging should be evaluated by EEG for nonconvulsive status epilepticus (NCSE).

DIAGNOSIS of seizure is obvious with marked motor activity, but can be suspected by subtle motor activity, spontaneous nystagmus, or unexplained encephalopathy.

The differential diagnosis of seizures with systemic infection includes:

Studies can include:

Long-term EEG monitoring is increasingly available in hospitals with neurology services, either as a mobile EEG device or with at least two channels on bedside monitors. An EEG machine with video capture is preferable; this may obviate transfer to an epilepsy monitoring unit (EMU).

CSF analysis should be obtained for most patients with seizure and sepsis unless there is another definite cause (e.g., cerebral infarction, abscess). Even then, septic emboli or meningitis should be considered.

Focal Deficits

Focal deficits are occastionally seen in patients with sepsis, but they may be missed because of encephalopathy. Focality can be due to a host of etiologies, but principal concern is focal structural lesion or the rare possibility of focal nonconvulsive discharge. Pre-existing (i.e. not acute) neurologic lesion is a common cause of focal findings in this setting.

PRESENTATION is of a patient with sepsis or SIRS noted to have weakness of one or more limbs or the face. Anatomic localization guides diagnostic study:

DIAGNOSIS is suspected by any focal deficit in a patient with sepsis or SIRS, and clinical anatomic localization directs the diagnostic studies.

•MRI or CT brain: Hemiparesis

•MRI spine: Paraparesis or quadriparesis

•Nerve conduction studies (NCS) and EMG: Weakness involving all extremities with or without the face.

•EEG: Focal weakness without a structural etiology

•LP: Focal or multifocal weakness without structural etiology

•MRI brachial plexus: Unilateral arm weakness

•MRI lumbosacral plexus: Unilateral leg weakness

Plexus lesion⁵ is suspected by prominent pain that involves the extremity more than the spine. Spinal lesions producing unilateral limb symptoms usually have significant regional spine pain and also are likely to have a distribution restricted to one or two dermatomal levels, whereas plexus lesions are more likely to span at least two or three dermatomal distributions.

CANCERS

Most neurologic complications related to cancer that we see are from metastases, but remote effects are the most difficult to diagnose.

The role of the hospital neurologist is largely to help with localization and diagnosis in these patients and to help with management of the neurologic complications of cancers: e.g. pain, seizure, altered mental status, cerebral edema. The hospital neurologist can also help to direct and facilitate therapy especially when time is of the essence (e.g., cord compression or malignant cerebral edema). Management of neurologic complications of cancer is discussed in Chapter 25.

Cancers can present to the neurologist through the following basic mechanisms:

Related posts:

Overview of Hospital Neurology Dizziness, Vertigo, and Imbalance Brain Death and Persistent Vegetative State Demyelinating Diseases Nutritional Deficiencies and Toxicities Developmental and Genetic Disorders

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