8/22/2016

Treatable Causes of Dementia


By: , Posted on: August 9, 2016
encyclopedia of neurological sciences
Dementia is an acquired progressive cognitive impairment leading to interference with daily activities. Although Alzheimer’s disease is the most common cause of dementia in the elderly, dementia can be caused by several other neurodegenerative etiologies as well as vascular, infectious, toxic, metabolic, traumatic, neoplastic, or inflammatory causes.
The term dementia is derived from the Latin de (out of), men (mind), and tia (state of) and literally refers to a state of being out of one’s mind. When used currently, it refers to an acquired cognitive impairment involving multiple domains of function in the absence of a clouding of consciousness. During the past two decades, the concept of dementia has evolved from a unitary disease that describes a global cognitive impairment to its present use as an umbrella term for a number of distinctive disease entities. The recent development of symptomatic treatment options and the possibility of future treatments aimed at halting or reversing the disease processes have highlighted the importance of early and accurate diagnosis of specific dementia syndromes.
Although a large number of neurological diseases can cause dementia (Table 1), many of these are very rare. Alzheimer’s disease (AD) and vascular dementia account for most cases, especially in elderly populations. The relative frequencies of different dementia diagnoses are illustrated in Figure 1.
able 1
Figure 1. Relative frequencies of different dementia frequencies in patients: (a) younger than 65 years old and (b) older than 65 years old. AD, Alzheimer's disease; DLB, dementia with Lewy bodies; FTD, frontotemporal dementia; VaD, vascular dementia. Adapted with permission from Galton CJ and Hodges JR (1999) The spectrum of dementia and its treatment. Journal of the Royal College of Physicians of London 33: 234–239.
Figure 1.
Relative frequencies of different dementia frequencies in patients: (a) younger than 65 years old and (b) older than 65 years old. AD, Alzheimer’s disease; DLB, dementia with Lewy bodies; FTD, frontotemporal dementia; VaD, vascular dementia.
Adapted with permission from Galton CJ and Hodges JR (1999) The spectrum of dementia and its treatment. Journal of the Royal College of Physicians of London 33: 234–239.
The most commonly used general diagnostic criteria for dementia are those proposed by the American Psychiatric Association in the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV). These criteria define dementia as a syndrome consisting of progressive impairment in two or more areas of cognition (i.e., memory, language, visuospatial, reasoning and problem solving, and behavior) sufficient to interfere with work, social function, or relationships in the absence of delirium or major nonorganic psychiatric disorders. Below is a discussion for the possible treatable causes of dementia.

Treatable Causes of Dementia

Normal Pressure Hydrocephalus
Normal pressure hydrocephalus (NPH) often presents with the classical triad of cognitive impairment, urinary incontinence, and gait apraxia with associated significant ventricular enlargement out of proportion with cortical atrophy on imaging studies. The cognitive profile is one of marked slowing, and the apraxia is virtually confined to gait with the characteristic glued-to-the-floor ‘magnetic’ gait. The etiology in many cases is unclear, although some are secondary to head injury, subarachnoid hemorrhage, or meningitis. Although many patients with NPH respond to removal of cerebrospinal fluid at lumbar puncture, predicting which patients will respond to ventricular shunting procedures is far from reliable with MRI, and intracranial pressure monitoring fails to reliably predict outcome.
Chronic Subdural Hematoma
Chronic subdurals often present subacutely with a fluctuating level of consciousness, symptoms of increased intracranial pressure, and often focal signs. They commonly occur in individuals prone to falls, such as alcoholics, the elderly, and those with coexistent neurological conditions. Treatment is by surgical evacuation of the hematoma, although many recur.
Metabolic and Endocrine Disturbance
Many metabolic disturbances, such as hyponatremia, renal, or hepatic failure, may cause cognitive symptoms, although the features are usually more typical of delirium than dementia. Disease of the thyroid is common, especially in the elderly population, but dementia due to hypothyroidism is rare and most reported cases have been shown to have developed AD on follow-up. More commonly, hypothyroidism will present with cognitive symptoms associated with depression and psychomotor retardation.
Autoimmune Encephalopathies
There is increasing awareness of a group of inflammatory cognitive disorders known as autoimmune encephalopathies. These have gone by various other names including nonvasculitic autoimmune inflammatory meningoencephalitis. One such condition is Hashimoto’s encephalopathy, a condition of cognitive dysfunction and seizures associated with high concentrations of antithyroid antibodies, often with normal or near normal thyroid function. Other antibody-mediated encephalopathies may be paraneoplastic, or associated with an underlying malignancy.
Deficiency States
Vitamin B12 deficiency is the most commonly encountered deficiency state and is usually associated with pernicious anemia. The most frequent neurological features are spinal cord dorsal column damage and peripheral neuropathy. Cognitive features are less common and usually present as hypoactive delirium, confusion, or psychomotor retardation rather than dementia. Replacing B12, especially if the duration of symptoms is short, can improve cognitive deficits at least in part.
Infections
Infection of the central nervous system by the human immunodeficiency virus (HIV) is probably the most common cause of dementia in the young. Also known as the acquired immune deficiency syndrome dementia complex, HIV-associated dementia presents as a subcortical dementia with psychomotor slowing, memory disturbance, apathy, withdrawal, and associated spastic gait disorder and hyperreflexia. Because it is usually a late manifestation of HIV infection at a stage when opportunistic infection or neoplasms may be prevalent, investigation should be directed at excluding focal lesions such as toxoplasmosis, cryptococcal meningitis, cytomegalovirus encephalitis, diffuse infiltration by lymphoma, and progressive multifocal leukoencephalopathy. Treatment with antiretroviral agents has been shown to improve cognitive deficits.
This excerpt was taken from the chapter Dementia in the article by D. C. Perry from the Multi-Volume Reference Work Encyclopedia of the Neurological Sciences (Second Edition). The easy-to-use ‘encyclopedic-dictionary’ format of this four-volume set features alphabetic entries, extensive cross-referencing, and a thorough index for quick reference. The wealth of information provided makes this reference work a trusted source of valuable information for a wide range of researchers, from undergraduate students to academic researchers.

The Polio Crusade

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Erradicación de La poliomielitis

Polio Tricisilla Adaptada

March Of Dimes Polio History

Dr. Bruno

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A 41-year-old man developed an acute illness at the age of 9 months during which, following a viral illness with headache, he developed severe weakness and wasting of the limbs of the left side. After several months he began to recover, such that he was able to walk at the age of 2 years and later was able to run, although he was never very good at sports. He had stable function until the age of 18 when he began to notice greater than usual difficulty lifting heavy objects. By the age of 25 he was noticing progressive difficulty walking due to weakness of both legs, and he noticed that the right calf had become larger. The symptoms became more noticeable over the course of the next 10 years and ultimately both upper as well as both lower limbs had become noticeably weaker.

On examination there was wasting of the muscles of upper and lower limbs on the left, and massively hypertrophied gastrocnemius, soleus and tensor fascia late on the right. The calf circumference on the right exceeded that on the left by 10 cm (figure1). The right shoulder girdle, triceps, thenar eminence and small muscles of the hand were wasted and there was winging of both scapulae. The right quadriceps was also wasted. The wasted muscles were also weak but the hypertrophied right ankle plantar flexors had normal power. The tendon reflexes were absent in the lower limbs and present in the upper limbs, although the right triceps was reduced. The remainder of the examination was normal.

Figure 1

The patient's legs, showing massive enlargement of the right calf and wasting on the left

Questions

1
What is that nature of the acute illness in infancy?
2
What is the nature of the subsequent deterioration?
3
What investigations should be performed?
4
What is the differential diagnosis of the cause of the progressive calf hypertrophy?

Answers

QUESTION 1

An acute paralytic illness which follows symptoms of a viral infection with or without signs of meningitis is typical of poliomyelitis. Usually caused by one of the three polio viruses, it may also occur following vaccination and following infections with other enteroviruses.1 Other disorders which would cause a similar syndrome but with upper motor neurone signs would include acute vascular lesions, meningoencephalitis and acute disseminated encephalomyelitis.

QUESTION 2

A progressive functional deterioration many years after paralytic poliomyelitis is well known, although its pathogenesis is not fully understood.2 It is a diagnosis of exclusion; a careful search for alternative causes, for example, orthopaedic deformities such as osteoarthritis or worsening scoliosis, superimposed neurological disorders such as entrapment neuropathies or coincidental muscle disease or neuropathy, and general medical causes such as respiratory complications and endocrinopathies.3

QUESTION 3

Investigations revealed normal blood count and erythrocyte sedimentation rate and normal biochemistry apart from a raised creatine kinase at 330 IU/l (normal range 60–120 IU/l), which is commonly seen in cases of ongoing denervation. Electromyography showed evidence of denervation in the right APB and FDI with polyphasic motor units and complex repetitive discharges, no spontaneous activity in the left calf and large polyphasic units in the right calf consistent with chronic partial denervation. Motor and sensory conduction velocities were normal. A lumbar myelogram was normal. Magnetic resonance imaging (MRI) scan of the calves is shown in figure2.

Figure 2

Axial T1 weighted MRI scan (TR 588 ms, TE 15 ms) of the calves, showing gross muscle atrophy and replacement by adipose tissue on the left, and hypertrophy of the muscles on the right, with only minor adipose tissue deposition

QUESTION 4

The differential diagnosis of the progressive calf hypertrophy is given in the box.

Causes of calf muscle hypertrophy

Chronic partial denervation

  • radiculopathy

  • peripheral neuropathy

  • hereditary motor and sensory neuropathy

  • spinal muscular atrophy

  • following paralytic poliomyelitis

    Neuromyotonia and myokymia

  • Isaac's syndrome

  • generalised myokymia

  • neurotonia

  • continuous muscle fibre activity due to: chronic inflammatory demyelinating polyradiculopathy, Guillain Barre syndrome, myasthenia gravis, thymoma, thyrotoxicosis, thyroiditis

    Muscular dystrophies

    Myositis

    Infiltration

  • tumours

  • amyloidosis

  • cysticercosis

    Link here