Approach to encephalopathy (acute and subacute): Clinical sciences

Encephalopathy refers to a change from baseline cognitive status, which can range from mild confusion to a comatose state.

Now, acute or subacute encephalopathy refers to cognitive impairment that has occurred over the last three months.

Based on the underlying cause, encephalopathy can occur as a result of primary neurologic conditions, but also due to non-neurologic causes, including toxins, metabolic derangements, nutritional deficiencies, and infections.

Alright, when a patient presents with chief concerns suggestive of acute or subacute encephalopathy, first perform an ABCDE assessment to determine if they are stable or unstable.

If unstable, stabilize the airway, breathing, and circulation. You might also need to intubate the patient and provide mechanical ventilation. Next, obtain IV access and consider IV fluids. Finally, put your patient on continuous vital signs monitoring, including heart rate, blood pressure, and pulse oximetry. Don’t forget to manage high intracranial pressure or ICP, if needed.

Here’s a clinical pearl to keep in mind! Unstable patients with encephalopathy may have medical emergencies like status epilepticus or conditions associated with high intracranial pressure, such as intracranial hemorrhage. However, systemic conditions, like liver failure and sepsis, can also result in encephalopathy.

Now, let’s go back to the ABCDE assessment and focus on stable patients.

Your next step here is to obtain a focused history and physical examination. The patient or a loved one will report recent changes in cognition, level of consciousness, or behavior, typically over the last few days to weeks. Examples of such changes include drowsiness, memory loss, impaired attention, and paranoia. Additionally, the physical exam reveals altered mental status, sometimes in combination with focal neurologic deficits.

These findings are highly suggestive of acute or subacute encephalopathy, so be sure to obtain labs, including a CMP and TSH level.

If the sodium, glucose, or TSH levels are extremely high or low, or if you identify elevated levels of liver enzymes, BUN, or creatinine, you are probably dealing with metabolic encephalopathy.

Some important conditions associated with abnormal glucose levels include diabetic ketoacidosis and hyperosmolar hyperglycemic state.

On the flip side, if the initial labs are normal, assess for toxin exposure. History might reveal medication or substance overdose or exposure to toxins like heavy metals or carbon monoxide. If this is the case, diagnose toxic encephalopathy.

Now, if you rule out toxic encephalopathy, assess the history and physical exam findings for episodes suspicious of seizures. If the patient or a loved one report waxing and waning mental status, repeated episodes of altered mental status, or episodes of jerking and shaking movements, consider seizures as the underlying cause.

To confirm, obtain an electroencephalogram, or EEG for short. If the EEG reveals patterns suggestive of seizures, you have your diagnosis. Keep in mind that encephalopathy can be present during a seizure, but also after a seizure, during the post-ictal state.

Next, if there are no signs of seizures, you should think of CNS infections.

In this case, history will reveal headache, confusion, and fever, sometimes in combination with neck stiffness, nausea, vomiting, and light sensitivity.

On the exam, you might notice focal neurologic deficits and signs of meningeal irritation, such as nuchal rigidity. Also, you might identify a positive Brudzinski sign, which refers to the flexion of the hip and knees when the neck is passively flexed; and a positive Kernig sign, which is pain on knee extension after holding the hip and knees in a flexed position.

With these findings, consider CNS infection and perform a lumbar puncture to analyze the CSF. But wait, there’s a catch! Before proceeding with lumbar puncture, be sure to rule out signs of increased intracranial pressure to avoid possible complications such as brain herniation.

Now, if CSF analysis shows an elevated white blood cell count, elevated protein level, and positive culture or PCR, the underlying cause is a CNS infection, such as meningitis or encephalitis.

Keep in mind that infections outside of the CNS can also cause encephalopathy, so always consider obtaining blood- and urine cultures as a part of your workup.

Okay, if there is no CNS infection, you should assess the patient for a stroke or mass lesion by obtaining brain imaging with a CT or MRI.

In order to cause encephalopathy, a stroke or brain mass must either be large enough to cause mass effect or they must affect a particular part of the brain, such as the frontal and temporal lobes, bilateral cortices, bilateral thalami, or the brainstem.

First, let’s focus on stroke, which is associated with acute, simultaneous onset of symptoms, such as difficulty speaking or understanding language, decreased level of consciousness, weakness or numbness, vision changes, and loss of coordination.

If the brain imaging shows ischemic or hemorrhagic lesions, diagnose stroke as the underlying etiology.

On the other hand, if the patient reports progressive worsening of symptoms, a headache, possibly with a fever and generalized malaise, and imaging shows an enhancing mass lesion, diagnose a brain mass as the underlying cause. The mass could be an abscess or a tumor.