A Form of Dementia that Affects Vision: Posterior Cortical Atrophy
Posterior cortical atrophy (PCA), also called Benson's syndrome, is a form of dementia which is usually considered an atypical variant of Alzheimer's disease (AD). The disease causes atrophy of the posterior part of the cerebral cortex, resulting in the progressive disruption of complex visual processing.
“…She Doesn’t See Them”
“Her car keys are right in front of her and she doesn’t see them,” her husband complained. “Maybe it’s a blessing in disguise, because I’m worried about her driving too. She scraped the side of the garage twice last week when she was parking. She just got a new pair of glasses, but they haven’t helped a bit.”
Mrs. W* looked at the ground, embarrassed. She knew her husband’s concern was a reflection of his love and frustration. At age 59, she thought she was young to have Alzheimer’s disease (AD), but also felt certain that something was wrong with her thinking. She was getting more and more worried about this. Neuropsychiatric assessment found her memory to be only mildly impaired, but her ability to look at a cluttered picture and locate specific details was not as good as expected. She was sent for an MRI scan of the brain, which indicated some shrinkage in the back of the brain, called the occipital lobes. In that same brain region, her use of glucose, the brain’s energy fuel, was reduced based on the results of a PET scan.
Posterior Cortical Atrophy
Mrs. W’s condition is called Posterior Cortical Atrophy (PCA). This form of dementia is easy to overlook. The key feature is usually visual problems without any discoverable eye disease, combined with cognitive problems that are milder than AD at the beginning. In Mrs. W’s case, her most noticeable visual problem was difficulty “seeing” more than one thing at a time, a symptom that is called “simultanagnosia.” In addition, she was younger than the typical AD patient and her memory and insight were only mildly diminished. She had none of the other findings or medical conditions, such as stroke, that might suggest a different diagnosis, and her imaging showed deterioration (atrophy) in the expected part of the brain.
PCA was first described in 1902, by the neurologist Arnold Pick. Since then, others have added to our knowledge, but we know much less about PCA than AD because PCA is not common. It is estimated to be present in about one of every twenty patients with dementia.
Patients with PCA experience the onset of symptoms earlier than those with AD, often in their mid-50s to early 60s. Memory and insight can be relatively good during the early stages of the disease, so patients often present with visual concerns. The damage with PCA is especially severe in the posterior part of the brain, the occipital lobes, which is why the disease is called posterior cortical atrophy. The occipital lobes help us understand what we see, so disease in that area creates visual problems. With PCA, a person may have trouble grasping the “big picture” or picking out something specific from a clutter of other objects. Things don’t look right, so the patient may first turn to an eye doctor, but examining the eyes or changing lenses doesn’t address the underlying brain problem.
In addition to visual and memory changes, PCA patients can show significant behavioral changes. Anxiety and irritability are the most common. Apathy or depression occurs about as often as with AD. If the use of antipsychotics is considered as a treatment for hallucinations or other symptoms, care must be taken to recognize the risks of this class of medications use with dementia patients in general and DLB patients in particular.
Because of its early onset, PCA affects people still busily involved in their careers and even parenting responsibilities. The frustration of not being able to do things like driving, anxiety over loss of independence, and fear for the future can be very intense and depressing.
Looked at through the microscope, PCA is often determined to be a form of AD. Autopsy of PCA patients show plaques and tangles in the occipital lobes and other brain areas typical for AD. Sometimes, though, the syndrome is an early version of other dementias such as dementia with Lewy bodies (DLB) or corticobasal degeneration.
This may not be clinically apparent, though the presence of hallucinations makes it very likely that the cause is DLB rather than AD.
Brain imaging is useful in establishing the diagnosis of PCA. Early on, an MRI will typically show atrophy in the posterior part of the brain that is out of proportion to atrophy in other parts of the brain. FDG-PET, a measure of brain metabolism, will show reduced activity in the same brain region. In the PCA cases due to AD, PET-amyloid scans will show accumulation of amyloid in the posterior portion of the brain as well.
Treatment and Other Helpful Guidelines
Mrs. W’s treatment team worked with her husband and her to preserve her independence, self-esteem, and quality of life as fully as possible. Although no medications carry a specific FDA indication or have been proven effective in reducing PCA symptoms, doctors often prescribe cholinesterase inhibitors such as donepezil (Aricept), rivastigmine (Exelon), or Razadyne (galantamine) or the glutamatergic medication memantine (Namenda). This makes sense because AD plaques and tangles are so often the underlying cause of PCA.
Modifying the Home
As with AD, the clinical management of PCA goes far beyond the use of medication. A geriatric care manager in communication with Mrs. W’s treatment team helped to make her home a safer place for someone with her visual difficulties. Clutter was removed, and labels were applied to drawers so that she could find things more easily. Throw rugs were removed or replaced with non-skid floor coverings. Stickers were put on glass doors and large windows so that Mrs. W would see them more easily. Adequate lighting was arranged in all rooms with attention to reducing glare.
Other Helpful Tips
Mrs. W voluntarily stopped driving. She let Mr. W help her with the bills and checkbook. She asked her husband to be her power of attorney and health care proxy so as to simplify management of their affairs and to make health care decisions in the event that she became unable to do so. She asked her husband, too, to help her load pills into her clearly labeled week-at-a-time pill box. Medications not currently in use were removed from the medicine cabinet to avoid confusion. To support Mrs. W’s ability to communicate with others and to obtain help if she ran into difficulties, she replaced her complicated smart phone with a simpler one. The new phone had fewer functions but a more readable face. Her husband and her doctor were put on “speed dial.”
As with AD, caregiver burden is difficult for those close to people with PCA. Because of its early onset, PCA imposes special and unique stresses. In addition, since PCA is uncommon, Mr. W was unable to find a support group in his area, but it was recommended that he join a group for early-onset AD, and he found a lot of comfort and practical advice by speaking with other caregivers there.
PCA is less common than AD, but it’s important to consider it as a cause of visual and cognitive symptoms in a relatively young person. With correct diagnosis, a treatment team can provide explanation and support that takes into account PCA’s special features. The care of a person with PCA requires careful attention to safety considerations, lifestyle changes, and planning for the future. PCA is not yet a curable condition, but an informed treatment team can lighten the burden for patient and caregivers.
*To protect anonymity and to illustrate features of PCA, Mrs. W’s story is a composite of symptoms from various patients. If you would like more information about Memory Matters programs and services call us at: 435-319-0407 or email us at email@example.com