How Pilocytic Astrocytoma Is Diagnosed

Pilocytic astrocytomas are slow-growing tumors usually found in children. They are diagnosed using a combination of imaging and biopsy. 

This article discusses the ways pilocytic astrocytomas are diagnosed.

Physical Examination 

A diagnosis of pilocytic astrocytoma begins with a review of your symptoms and medical history. Next, your or your child's healthcare provider—likely a pediatrician or pediatric neurologist—will perform a focused physical exam, checking the function of your cranial nerves and reflexes.

Hearing difficulties, vision changes, and nystagmus are signs pointing to a potential brain tumor.

Initial symptoms are usually nonspecific and related to increased intracranial pressure (ICP).

A funduscopic examination—a test that requires using a microscope to visualize the back of the eye—may reveal papilledema, a sign of ICP.

ICP may also present as gait disturbance (a change in how you walk), loss of balance and coordination, or difficulty walking.

Labs and Tests 

No lab tests can confirm pilocytic astrocytoma. Baseline laboratory tests such as a complete blood count (CBC) a, basic metabolic panel, and bleeding times (prothrombin time and activated partial thromboplastin time) may be obtained for general metabolic surveillance and preoperative assessment.

The following tests may help your healthcare provide confirm or rule out a pilocytic astrocytoma diagnosis:

• Biopsy: A biopsy involves taking a sample of the tumor tissue so that the cells can be analyzed under a microscope. A biopsy can help detect the presence of PA. Biopsy is commonly performed during brain tumor removal surgery.
• Electroencephalograms (EEG): An EEG looks at the delta waves of the brain which may give your provider clues about potential tumors within the cerebral hemispheres of the brain.
• Genetic sequencing: Genetic sequencing involves taking samples of cancerous tissue and examining its genetic makeup to determine the properties of these tumor cells.

Imaging 

Imaging scans are important in helping your provider determine the size and location of your pilocytic astrocytoma. Imaging scans may also help your provider rule in or rule out brain cancer by showing the presence or absence of specific tumor characteristics.

The following imaging techniques may be used to help diagnose PA:

• Magnetic resonance imaging (MRI): An MRI is a painless, noninvasive imaging technique that uses a powerful magnetic field, radio waves, and a computer to produce detailed pictures of the brain. MRI is the preferred imaging test for PA.
• Computed tomography (CT): A CT scan uses X-rays to provide a more detailed image of the brain and brain structures. A CT scan is particularly helpful in visualizing the cerebellum and deep structures of the brain that are common locations for pilocytic astrocytomas. A CT scan is usually performed when MRI is unavailable. 
• X-ray: An X-ray is a quick and inexpensive imaging tool that can be performed before a CT or an MRI if there is suspicion of a brain injury, tumor, or trauma.

Differential Diagnosis

The symptoms of PA are usually nonspecific, nonlocalized, and hard to differentiate from other conditions that impact the brain, therefore an extensive workup consisting of using different types of imaging and a high degree of clinical suspicion is needed to make an accurate diagnosis.

Your medical team will need to rule out other conditions when diagnosing PA, such as:

• Hemangioblastoma
• Medulloblastoma
• Meningioma
• Atypical teratoid or rhabdoid tumor (rare tumor)
• Ependymoma
• Ganglioglioma (low-grade tumor)
• Oligodendroglioma
• Craniopharyngioma
• Germinoma (tumor that begins in the germs cells)
• Langerhans cell histiocytosis
• Pleomorphic xanthoastrocytoma (rare type of brain tumor)
• Cerebellar hemorrhage (type of intracranial hemorrhage)
• Fibrillary astrocytoma (group of primary slow-growing brain tumors)
  

In adults, your medical team will have to rule out:

• Brain abscess: A pus-filled swelling in the brain
• Brain metastasis: Cancer that has spread from the original (primary) tumor to the brain
• Cardioembolic stroke: This presents with the sudden onset of neurological deficits that are maximal at onset
• Orbital cavernous hemangioma: A benign, noninfiltrative, slowly progressive vascular neoplasm composed of endothelial-lined spaces surrounded by a well-delineated fibrous capsule
• Encephalitis: An infection or inflammation of the brain

Summary

Pilocytic astrocytomas are slow-growing tumors usually found in children that are diagnosed clinically using a combination of imaging (computed tomography or magnetic resonance imaging) and biopsy.

A Word From Verywell

PA is a clinical diagnosis that requires a high degree of clinical suspicion, imaging tools—preferably MRI—and a biopsy that is performed during surgical removal of the tumor to confirm the diagnosis. 

If you or your child is experiencing signs of increased cranial pressure—like headache, vision changes or nausea and vomiting, seek immediate medical attention. Early diagnosis allows you and your provider to create a customized treatment plan that will help you to achieve your goals and the best prognosis.