Approach to differentiating lesions (cerebellum): Clinical sciences

The cerebellum, which is the major control center for the coordination of voluntary movements and balance, is connected via multiple pathways to the cerebrum, brainstem, and the spinal cord. Conditions that can affect the cerebellum and these connecting pathways can be subdivided into acute, subacute, and chronic cerebellar lesions.

Now, if your patient presents with chief concerns suggestive of a cerebellar lesion, first perform an ABCDE assessment to determine if they are stable or unstable. If unstable, stabilize the airway, breathing, and circulation. In some cases, you might even have to intubate the patient and start mechanical ventilation. Next, obtain IV access and consider starting IV fluids. Finally, put your patient on continuous vital sign monitoring, including heart rate, blood pressure, and pulse oximetry, as well as cardiac telemetry.

Alright, let’s go back to the ABCDE assessment and focus on stable patients. In this case, obtain a focused history and physical examination. These patients will report a loss of coordination, such as difficulty walking, keeping balance, sitting up straight, or using their arms to pick up objects. They might also report a room spinning dizziness with nausea and vomiting; difficulty focusing their vision; slurred speech; or difficulties with swallowing.

On the exam, you will find limb-, truncal-, or gait ataxia, which refers to the loss of coordination of voluntary movement. Limb ataxia, which is predominantly seen with cerebellar hemispheric lesions, is associated with dysmetria on finger-to- nose or heel-to-shin testing. For example, on the finger-to-nose test, the patient might point past the target as they are unable to judge the distance properly, known as past-pointing. Another example of limb ataxia is dysdiadochokinesia on rapid alternating movements, which can be tested by asking the patient to alternate supinating and pronating their arms.

On the flip side, truncal ataxia, which is most prominent with cerebellar vermis lesions, is associated with severe truncal swaying when the patient is trying to sit or stand up straight; or titubation, which is an anterior-posterior rhythmic tremor of the head or upper trunk.

Finally, gait ataxia is characterized by a wide-based, unsteady gait with an irregular rhythm and inconsistent stride length. Gait ataxia is especially obvious during tandem testing. Perform this test by asking the patient to walk with the heel of one foot touching the toes of the other foot with each step, as if they were walking on a tightrope.

In addition to ataxia, you might find abnormal eye movements due to lesions of the flocculonodular lobe of the cerebellum. Some important findings include nystagmus, as well as impaired smooth pursuit and saccades.

Nystagmus is rhythmic, rapid eye movements with a fast phase in one direction and a slow phase in the opposite direction. Examples of pathologic nystagmus consistent with a central nervous system lesion include vertical nystagmus and direction-changing nystagmus.

Impaired smooth pursuit is the inability to smoothly follow a moving object, while impaired saccades refer to the inability to rapidly change the fixation of vision from one stationary object to another.

There might be abnormal speech, such as dysarthria, or scanning speech, which is an abnormal speech pattern that is slow, with words broken up into syllables in different intonations. Lastly, you might find an intentional tremor, a side-to-side tremor of the arm that worsens upon reaching the intended target; or a postural tremor while holding the arms in position. With these findings, consider a cerebellar lesion, so your next step is to assess the time course of symptoms.

If the onset of symptoms is acute, assess whether the symptoms are unilateral or bilateral. With unilateral symptoms, consider cerebellar stroke as the underlying cause and obtain imaging of the brain with CT or MRI.

If there is a stroke involving the superior aspect of the cerebellum and the superior cerebellar peduncle, diagnose a superior cerebellar artery stroke. If you identify a stroke in the anterior inferior cerebellum and middle cerebellar peduncle, diagnose an anterior inferior cerebellar artery stroke. Finally, if the stroke is in the posterior inferior cerebellum and inferior cerebellar peduncle, diagnose a posterior inferior cerebellar artery stroke.

Here's a clinical pearl! The posterior inferior cerebellar artery also supplies the lateral medulla, so the patient might present with lateral medullary syndrome, also known as Wallenberg syndrome. In addition to ataxia, these patients will have dysphagia, hoarseness, decreased pain and temperature sensation in the ipsilateral face and contralateral body, and ipsilateral Horner syndrome.

Next, let’s discuss a patient with acute-onset bilateral symptoms. In this case, consider acute cerebellitis, which is more commonly seen in children. Various infectious agents are associated with this condition, particularly varicella-zoster virus, Epstein-Barr virus, Coxsackie virus, herpes simplex virus, and Mycoplasma pneumoniae.

To confirm your diagnosis, obtain a brain MRI. The patient will report nausea and vomiting, headache, confusion, recent illness, and possibly persistent fever. On the exam, you will find altered mental status and ataxia of the limbs, trunk, and gait, while the MRI will show abnormally increased signal and edema of the cerebellum. With these findings, diagnose acute cerebellitis,