If you’ve taken Dilantin for a long period of time or at a high dose, you could develop Dilantin cerebral atrophy.

Dilantin (phenytoin) is an anti-seizure medicine that was invented in 1908 by a German chemist. By 1940, Dilantin was used to treat epileptic seizures, and in the 1960s, patients began taking it for anxiety and depression.

Seizures occur when brain cells communicate faster (neurons fire quicker) than they should. Dilantin works by keeping the brain cells from firing at the speed needed to initiate a seizure. Unfortunately, research indicates Dilantin cerebral atrophy can be a side effect of controlling these seizures because some of the brain cells lose neurons that connect the cells to each other.

Indications of Dilantin Cerebral Atrophy

The area most likely affected by a loss of neural activity is the cerebellum. Dilantin cerebral atrophy that concentrates on the degeneration of the cerebellum is specifically known as cerebellar atrophy.

The cerebellum, located at the base of the brain above the brain stem, is the part of the brain that controls coordinated movement and speech. The cerebellum is made of two sections of tissue that fold together in the middle. The right side of the cerebellum controls movement on the right side of the body, and the left side of the cerebellum initiates movement on the left.

Symptoms of cerebellar atrophy vary and depend upon the severity of the deterioration. Indications include:

• Inability to complete smooth, precise movements
• Tremors
• Lack of balance
• Uncontrolled and rapid eye movements
• A lurching gait
• Unsteady or stumbling walk
• Inability to stop bobbing up and down upon sitting
• Trouble completing daily tasks such as brushing teeth and buttoning clothes
• Changes in the tone, pitch or volume of the voice
• Headaches
• Dizziness
• Personality changes

It is documented that years of seizures can result in brain deterioration, but research has shown long-term phenytoin use can result in Dilantin cerebral atrophy.

In a 1994 study, researchers found the cerebelli of patients on Dilantin were notably smaller when compared with patients who had never taken the medication. The study was conducted by examining the MRI results of all patients involved.

In 2003, another study determined that patients who were on Dilantin for an extended period of time incurred moderate to severe atrophy of the cerebellum.

According to Radiopaedia.org, nearly 30 percent of patients who use Dilantin for a long time will eventually see deterioration of the cerebellum. Many of these patients also will experience a corresponding thickening of the skull, known as calvarial thickening. This side effect is responsible for appearance of coarse features and thickened forehead area among the population affected by cerebellar atrophy.

The calvaria is the skullcap, which consists of the frontal bone, occipital bone, and parietal bones. According to the American Journal of Roentgenology, the increased thickness in the calvaria is most often found in the diploic space, which is the expansion of the spongy bone between the inner and outer tables of the skullcap among Dilantin patients.

One study of 93 women, ranging in ages 18 to 40 years old, who took Dilantin found that they suffered femoral neck bone loss after one year of taking the drug. According to Medscape, women on Dilantin showed a bone loss of 2.6 percent at the femoral neck.

The study, led by first author Alison M. Pack, MD, from Columbia University in New York was published in the April 29, 2008 issue of Neurology.

“This amount of bone loss, especially if it continues over the long term, could put these women at increased risk of fractures after menopause,” Dr. Pack said in a statement from the American Academy of Neurology. The statement also said that femoral neck fractures have been associated with a higher risk of death in elderly patients.

In certain cases that are caught early, some patients can see an improvement in their cerebellar atrophy symptoms as they are withdrawn from Dilantin while overseen by a doctor. Dilantin is such a potent medication that even a slight change in the dose can lead to it either being ineffective or being toxic. Any change in dosing must be overseen by a doctor.

The FDA says blood serum levels should be checked immediately upon the first sign of acute toxicity.

“Dose reduction of phenytoin therapy is indicated if serum levels are excessive; if symptoms persist, termination is recommended,” says the FDA.

Patients with more severe symptoms of cerebral atrophy for a long period of time will less likely be able to fully recover. Loss of muscle coordination is the issue most likely to prove irreversible.