Not all dementia is Alzheimer: Dementia with Lewy bodies
David Knopman, MD and
Janet Jankowiak, MD
Dementia with Lewy bodies (DLB) can be a tricky disease to understand.In simple terms, DLB is a combination of dementia and Parkinsondisease (PD). Dementia refers to a problem with normal dailyactivities due to problems thinking (see "About dementia andsimilar conditions" on the following page). The most commonproblems in dementia are short-term memory loss, lack of drive,and slowed thinking. PD typically includes a tremor (shaking)that is present at rest, slowed movements, and loss of facialexpression. People with PD have a characteristic walk: theyare stooped over, don't swing their arms normally, take small,shuffling steps, and may lose their balance.
Lewy bodies are seen in brain tissue viewed under the microscope.They are known to be the hallmark of PD. They usually occurin a part of the brain known as the substantia nigra deep withinthe brain, but also sometimes occur in other brain locations.The significance of Lewy bodies found outside the substantianigra was not appreciated until recently. Also, Lewy bodiesin the brain were previously thought to indicate PD, and nothingelse.
About 20 years ago, neurologists and neuropathologists (scientistswho study the structure of the brain) came to recognize thatLewy bodies were also found in patients with a dementing illnessthat often had been called Alzheimer disease (AD) when the patientwas first diagnosed. New insights led to more careful observationsabout the distinctive features of DLB. In 1996, Dr. Ian McKeithand coworkers brought together a group of scientists interestedin defining DLB.1 Their first publication identified some corefeatures of what they called DLB. These included dementia, parkinsonism(features that look like PD), marked variations in arousal,hallucinations, and extreme sensitivity to antipsychotics (medicationsused to treat hallucinations and psychosis).
From that starting point in 1996, the joint efforts of neurologists,psychiatrists, sleep physicians, and neuropathologists haveled to a blossoming of understanding of DLB. Much progress hasbeen made in characterizing and treating DLB. DLB is actuallymore than just dementia and PD. In this issue of Neurology,Dr. McKeith and an international group of clinicians and researchersreport on their efforts to better define the clinical and anatomicfeatures of the disease.2 They also outline some of the treatmentchoices for the disorder.
The thinking problems in DLB include problems with memory justlike in AD, but the memory difficulties in DLB are milder thanin AD. In many patients with DLB, attention and concentrationare somewhat more affected compared to AD.
The problems with movement in DLB can be very much like typicalPD. Slowness of movement and thinking is quite common in DLB.Walking and balance problems are very prominent in DLB, andfalls are common. Tremor is less common in DLB than in typicalPD.
DLB has some other unique features as well. From day to day,many patients with DLB experience marked fluctuations in howalert they are. These patients may seem very confused one dayand very sharp the next. Many patients with DLB experience dramatic,detailed visual hallucinations. These resemble dreams in theirvividness and their detachment from reality. DLB patients alsoexperience a peculiar sleep disorder called REM sleep behaviordisorder, known as RBD. RBD can occur years before the diagnosisof DLB is made. In RBD, patients experience frightening dreams.They thrash about in their sleep, may strike their bed-partners,and may fall out of bed.
Patients with DLB also exhibit a remarkable sensitivity to many,but not all, antipsychotic medications such as haloperidol orrisperidone. Because DLB patients either have PD or are on theverge of it, they are very sensitive to the Parkinson-causingside effects of this class of medication.
There are many aspects to DLB that make it challenging to manage.Fortunately, there are treatments for the thinking and movementproblems, the hallucinations, and the sleep disorder. Developingan integrated approach to these problems can be tricky. Treatmentfor one of the features of the disease can worsen others. Withthe increased understanding of DLB provided by McKeith and coworkers,physicians have much more to offer patients with DLB and theirfamilies.
Dementia is the diagnosis (label) given when a person has problemsthinking and remembering, which interfere with his/her normaldaily functioning.
When a neurologist first sees a person for possible dementia,he/she first considers whether there could be some other conditioncausing the problems. Three other conditions that can be confusedwith dementia are delirium, depression, and mild cognitive impairment.
When a person rapidly develops confusion and changes in thinking,neurologists call this delirium. Examples are intoxication withalcohol or other drugs and infections involving the brain. Fortunately,this condition generally resolves when the underlying causeis fixed or resolves. In contrast, dementia usually developsmuch more slowly and the underlying cause may not be obviousor correctable. Usually it is possible to separate dementiafrom delirium. However, some patients with dementia with Lewybodies (DLB) experience fluctuations and periods of heightenedconfusion that can look like delirium.
The key feature of depression is the obvious dramatic appearanceof sadness and low mood. Depression is often accompanied bypoor concentration, poor attention span, and poor memory, whichmay suggest dementia. However, people with depression oftencomplain constantly about their memory. On the other hand, peoplewith dementia generally do not complain about problems withmemory because they are unaware of the problem. In the earlystages, people with dementia even may make excuses for why theyforgot something. Patients with DLB, and people with other typesof dementia, may have dementia and depression at the same time.
Mild cognitive impairment is also a disorder of thinking, butdaily functioning is still preserved. In contrast, patientswith dementia have problems with their normal daily activities.Some people with the features of DLB, such as problems withbalance and sleep, may not have dementia, but instead may havemild cognitive impairment. Neurologists believe that mild cognitiveimpairment is a stage just before the development of true dementia.
Alzheimer disease (AD) is the most common form of dementia.AD makes up about 60% to 80% of all dementia. About 30% of patientswith AD go on to develop PD. Many of these people will haveDLB. Under the microscope, it is common to see changes in thebrain, both of AD and DLB in the same person.
Stroke can cause dementia. Vascular dementia is the name givenwhen strokes are the main cause of dementia. Strokes can alsocause problems with walking, balance, vision, and speech.
Some medications can affect thinking and memory. Examples aremedications to treat sleep problems and anxiety. These drugsare easily capable of making a person slow down mentally, andtherefore activities that require full alertness (such as driving)should be avoided while on these medications. Medications forpain often have similar effects. Some medications such as theantipsychotic drugs (used to treat hallucinations and psychoticbehavior) can cause many of the symptoms of PD (especially slowedmovements and sometimes slowed thinking). Because every personis unique, it is not always possible to predict what side effectsmay occur.
A wide variety of abnormal levels of substances carried in theblood, including nutrients and hormones, can cause deliriumor dementia. The most common disorders that cause delirium areabnormal levels of sodium and calcium, serious loss of kidneyor liver function, major declines in thyroid hormone levels,and severe decreases in levels of vitamin B12 in the blood.Because delirium and dementia can be difficult to tell apartat times, neurologists check for these abnormalities. They areall easy to diagnose with inexpensive blood tests and are oftentreatable.
A condition known as normal pressure hydrocephalus (NPH) canmimic DLB. NPH is a very rare condition that causes a distinctiveproblem in walking, loss of bladder control, and dementia. ACT scan or MRI of the brain of a patient with NPH shows dramaticenlargement of the brain ventricles (the fluid-filled innercavities of the brain) out of proportion to the apparent shrinkageof the brain itself. In appropriate patients, a tube can beplaced surgically inside the brain ventricles to drain the excessCSF. In the right patient, ventriculoperitoneal shunting, asthe procedure is called, can bring considerable improvementin walking, bladder control, thinking, and memory.
A head injury, even relatively mild, may cause problems thatmimic dementia. A fall or bump to the head may cause blood clotsto form between the brain and the inner side of the skull (calleda subdural hematoma). These are particularly common in olderpeople who fall or bump their head and do not think the injuryis serious or even forget about it. Often there may be rebleedingwithin the subdural hematoma with progressive or more rapidloss of mental function. Removal of the subdural hematoma bysurgery can cure the symptoms of memory loss and in other casescan be life-saving.
There are many conditions that can mimic dementia and many differentcauses of dementia. It is important to seek medical help earlywhen problems with thinking occur, because treatments are available.
McKeith IG, Galasko D, Kosaka K, et al. Consensus guidelines for the clinical and pathologic diagnosis of dementia with Lewy bodies (DLB): report of the consortium on DLB international workshop. Neurology 1996;47:1113–1124.[Abstract/Free Full Text]
McKeith IG, Dickson DW, Lowe J, et al. Diagnosis and management of dementia with Lewy bodies: third report of the DLB consortium. Neurology 2005; 65:1863–1872.[Abstract/Free Full Text]
Top.
What are Lewy bodies?
What are the unusual...
