Chapter 16 - Dementia

Questions

Define the following terms:

dementia, Alzheimer disease, amnesia, Creutzfeldt-Jacob disease, Huntington's disease, transcortical aphasia, dysinhibition, paratonia, gait apraxia, palmomental reflex, grasp reflex.
Dementia is a diffuse loss of cortical function.
Alzheimer disease is a cortical degenerative condition characterized by senile (amyloid) plaques and neurofibrillary tangles mostly affecting the temporal and parietal lobes.
Amnesia is a loss of memory.
Creutzfeldt-Jacob disease is an infectious condition due to prion proteins. It is characterized by subacute dementia, often accompanied by startle myoclonus, ataxia and cortical blindness.
Huntington's disease is an autosomal dominant hereditary disease characterized by choreoathetosis, behavioral symptoms and dementia.
Transcortical aphasia is a form of aphasia often seen in Alzheimer's disease in which repetition is spared but the ability to name objects presented to the patient (confrontational naming) is impaired.
Dysinhibition is a loss of normal inhibition of certain behavioral responses or reflexes.
Paratonia (gegenhalten) is an involuntary, irregular resistance to passive movements. It is a soft sign of cerebral cortical dysfunction.
Gait apraxia is an inability to generate the normal patterns of gait. The gait becomes simple with sliding the feet along the floor, and is described as "robotic" or "glue-footed." There may ultimately be retropulsion.
Palmomental reflex this is a primitive reflex in which scratching the palm results in wrinkling of the chin on that side. It is a soft sign of cerebral cortical dysfunction.
Grasp reflex is a primitive reflex (present in very young children) in which the fingers involuntarily flex when the palm is stroked, It is a sign of frontal cortical dysfunction.

16-1. What is a good working definition of dementia?

Answer 16-1. Dementia is defined as diffuse loss of cortical functions. By definition, there must be more than one cognitive function lost.

16-2. How can you test for the presence of dementia?

Answer 16-2. Testing involves various neuropsychological measures that define the loss of more than one type of cortical functions (not just memory, for example).

16-3. Are there any physical exam findings in dementia?

Answer 16-3. There may be some "soft" physical findings of frontal lobe damage (grasp reflex, gait apraxia, palmomental reflex, snout reflex, suck reflex) or diffuse cortical loss (paratonia, problems with upgaze).

16-4. What are the two basic types of dementia?

Answer 16-4. Dementia may be due to diffuse loss of cortical neurons (so-called "cortical dementia") or damage to subcortical structures ("subcortical dementia") that project to the cerebral cortex.

16-5. What is the most common cause of dementia?

Answer 16-5. The most common cause is Alzheimer's disease. It is very common, reaching about 40-50% of the population by age 85.

16-6. What is the second most common cause of dementia?

Answer 16-6. Multi-infarct dementia is the second most common cause of dementia.

16-7. What is the pathology of Alzheimer disease?

Answer 16-7. Neurofibrillary tangles and senile plaques, usually most prominent in the temporal lobes (and hippocampi) and parietal lobes.

16-8. What language problems are found in Alzheimer's disease?

Answer 16-8. Patients often have transcortical dysphasia (can repeat complex phrases but trouble with naming objects).

16-9. What are the characteristics of multi-infarct dementia?

Answer 16-9. There is usually stepwise deterioration in function (with strokes) and there may be specific areas of damage such as aphasia, hemianopsia, etc.

16-10. What are the characteristics of Creutzfeldt-Jacob disease?

Answer 16-10. Creutzfeldt-Jacob disease (akin to Bovine Spongiform Encephalopathy - mad cow disease) is rapidly progressive over months. It is due to a prion protein. There are symptoms of dementia with ataxia early on. Other signs may include amyotrophy and cortical blindness. Later on there are severe myoclonic jerks (often produced by startle).

16-11. What diagnostic tests are there for Creutzfeldt-Jacob disease?

Answer 16-11. The only definitive diagnosis is brain biopsy although recently it is possible to measure prion proteins in spinal fluid. The EEG may be helpful (regular, 1 per second triphasic waves).

16-12. What is Huntington's disease?

Answer 16-12. Huntington's disease is an autosomal dominant hereditary disease due to expansion of CAG repeats. Progressive symptoms may arise at any age (most common in middle age). The symptoms include the triad of choreoathetosis, behavioral symptoms and dementia. Movements and behaviors may improve slightly with neuroleptics (dopamine blockers), but there is definitive therapy.

16-13. What is normal pressure hydrocephalus (NPH)?

Answer 16-13. Normal pressure hydrocephalus (NPH) presents with gait disorder (ataxia), incontinence, and dementia, progressive over months. Dementia is usually the last symptoms to develop. The gait is apraxic (glue-footed, magnetic, robotic).

16-14. How can you diagnose normal pressure hydrocephalus (NPH)?

Answer 16-14. History and physical exam are paramount. There is a normal LP opening pressure. Imaging shows panventriculomegaly on CT or MR scan without prominent cortical atrophy. CSF drainage procedure (15-30 cc) followed by improved gait and bladder control is the best predictor of good response to therapy (shunting of CSF). The condition may be idiopathic or it may result from sequellae of bacterial meningitis, subarachnoid hemorrhage. Ventricular or lumbar shunt may help (50% improve; 40% morbidity).

16-15. What are some treatable causes of diffuse cortical dysfunction (dementia)?

Answer 16-15. Most common treatable causes include depression ("pseudodementia"), thyroid dysfunction, metabolic encephalopathy secondary to medications, hypoxia, nutritional deprivation, or dehydration (electrolyte and fluid imbalances). Rarely, it may be caused by: B12, thiamine or folic acid deficiency, anemia, subdural hematoma (usually bilateral), tumor, hyperlipidemia, chronic meningitis (cryptococcal, syphilitic), demyelinating disease, normal pressure hydrocephaly.