Paraneoplastic Cerebellar Degeneration (PCD)

How PCD develops

Some cancers produce proteins normally found only in the nervous system. The immune system recognizes these proteins on cancer cells and attacks them, but the same antibodies and immune cells (particularly T cells) also attack Purkinje cells in the cerebellum. These cells are lost permanently, which is why early treatment matters.

In many people, PCD appears before the cancer has been found, sometimes months to a few years earlier. The cancer is often small at that stage.

Antibodies and associated cancers

Some people have no identifiable antibody, but the clinical picture and cancer association still support the diagnosis.

Symptoms

Symptoms usually develop over weeks to a few months, which is faster than most degenerative ataxias:

• unsteady, wide-based walking and frequent falls
• clumsy arms and hands, with tremor when reaching
• slurred, slow or "scanning" speech
• dizziness or vertigo, nausea and vomiting at onset
• double vision and jerky eye movements (nystagmus)
• difficulty swallowing
• in some, memory changes, numbness or weakness when other parts of the nervous system are involved

Diagnosis

1. Excluding common causes of cerebellar ataxia: stroke, alcohol, medicines (such as phenytoin), vitamin deficiencies (B1, E), thyroid disease, multiple sclerosis and infections.
2. Brain MRI: often normal early; shrinkage of the cerebellum appears later.
3. Paraneoplastic antibody panel in blood and spinal fluid.
4. Lumbar puncture: may show inflammation.
5. Cancer search: CT of the chest, abdomen and pelvis, PET-CT, mammogram, pelvic ultrasound and other targeted tests. If no cancer is found, screening is repeated periodically (often every 4 to 6 months for 2 years).

Treatment

• Treat the cancer: surgery, chemotherapy, radiation or other therapies. This is the most important step and may stabilize the neurological condition.
• Immunotherapy: corticosteroids, IV immunoglobulin, plasma exchange, and sometimes rituximab or cyclophosphamide. Responses are more likely when started early, before Purkinje cells are lost.
• Rehabilitation: physical, occupational and speech therapy; walking aids; swallowing assessment.
• Symptom relief: medicines for vertigo, nausea or tremor in some cases.

Outlook

The outlook depends on the antibody type, how early treatment begins, and the cancer itself. Many people with anti-Yo or anti-Hu disease have lasting disability despite treatment. Those with anti-Tr or anti-mGluR1 antibodies and Hodgkin lymphoma more often improve after the lymphoma is treated. Early diagnosis gives the best chance of stabilizing symptoms.

Frequently asked questions

What is paraneoplastic cerebellar degeneration?

It is a rare condition in which the immune system, responding to a cancer, attacks the cerebellum. This causes rapidly worsening problems with balance, coordination, speech and eye movements. It is a type of paraneoplastic neurological syndrome.

Which cancers cause paraneoplastic cerebellar degeneration?

The most common are ovarian, breast and other gynecologic cancers, small cell lung cancer and Hodgkin lymphoma. Testicular cancer and others are less common. The specific antibody found often points to the type of cancer.

Can paraneoplastic cerebellar degeneration happen before cancer is diagnosed?

Yes. Neurological symptoms often appear months or even a few years before the cancer is found. Anyone diagnosed with PCD needs a thorough search for cancer, and repeated screening if none is found initially.

Is paraneoplastic cerebellar degeneration reversible?

Partial improvement is possible, especially with early cancer treatment and immunotherapy, and with some antibody types such as anti-Tr. Often the damage to cerebellar cells is permanent, and treatment aims to stop further decline.

What is anti-Yo syndrome?

Anti-Yo syndrome is paraneoplastic cerebellar degeneration associated with anti-Yo (PCA-1) antibodies. It typically affects women with ovarian, breast or uterine cancer and causes a severe cerebellar syndrome that develops over weeks to months.