Neurodegenerative Disease Dementia Miscellaneous Causes


Many other heterogeneous conditions have been shown to be involved in the reversible dementia pathogenesis. For example, dementia cases due to radiation or dialysis have been reported to reverse after appropriate treatment.26


The identification of such conditions is easier when patients’ previous history is considered.


New Causes of Reversible Dementias Epileptic Disorders


Transient epileptic amnesia is a syndrome characterised by recurrent, brief attacks of memory loss in middle-aged or older people, usually after sleep, associated with symptoms of temporal lobe epilepsy (automatisms, electroencephalogram findings, etc.). It is a benign syndrome that is responsive to antiepileptic medication, but complete resolution of cognitive symptoms is unusual.27


It has been suggested that a degenerative process exists in parallel with the epileptic disorder.28 Autoimmune Encephalopathies


With the discovery of antibodies such as anti-Yo, anti-Hu and anti-Ri, which are related to paraneoplastic disorders, the spectrum of potentially treatable dementias has been broadened. Also, a specific search for other antibodies – such as voltage-gated potassium channel antibodies in non-paraneoplastic encephalopathies and anti-N-methyl-d-aspartate receptor antibodies in paraneoplastic encephalopathies30,31


Autoimmune encephalopathies (or autoimmune dementias) is a newly proposed term for dementias underlying an autoimmune process. They constitute a heterogeneous group of disorders that may present with cognitive decline.29


– has demonstrated that reversible dementias


are not a myth. A favourable prognosis is achieved with resection of the underlying tumour and/or immunosuppression in paraneoplastic cases, and with appropriate management using immunosuppression in non-paraneoplastic cases.


Hashimoto’s encephalopathy is another potentially treatable disorder that presents as rapidly progressive dementia accompanied by myoclonus, epileptic seizures and altered level of consciousness. Brain computed tomography or MRI may be normal but thyroid antibodies (anti-thyroid peroxidase and anti-thyroglobulin) can be found in high titres. Steroid initiation is the treatment of choice, with immediate improvement (steroid-responsive encephalopathy).32


Obstructive Sleep Apnoea


Some patients referred to memory clinics are suffering from obstructive sleep apnoea. These patients are often younger and may represent around 5 % of patients under 65 years attending these clinics.33


Due to


the bad quality of sleep and the excessive daytime sleepiness, memory problems may be the first symptoms these patients experience. Improvement in memory is evident after treatment.


Inflammatory Vasculopathies


Other inflammatory or autoimmune diseases may present with central nervous system (CNS) involvement. Systemic lupus erythematosus, Sjögren’s syndrome, Behçet’s disease, antiphospholipid syndrome and sarcoidosis can affect CNS vasculature.34


is another condition that may initially present with cognitive symptoms.35


requires a high degree of suspicion.


Primary CNS angiitis is a rare autoimmune disease that typically presents in middle-aged people with headache, cognitive symptoms,


232 Medications Isolated CNS angiitis The diagnosis of these disorders is usually difficult and


There are several reports of drugs that have provoked cognitive impairment, especially in older people who are susceptible to polypharmacy and drug–drug interactions.42,43


Benzodiazepines,


antipsychotics, antiepileptics and tricyclic antidepressants have been accused of worsening memory and executive functioning. Newer and older antiepileptic drugs, such as topiramate and sodium valproate, have been implicated in worsening cognition.44,45


Cognitive symptoms


may be reversed after withdrawal of the responsible drug. Steroid psychosis is a well known adverse event of chronic steroid treatment. In


EUROPEAN NEUROLOGICAL REVIEW


HIV dementia is irreversible, but HIV-related neurocognitive impairment may be reversed by highly active antiretroviral therapy. Treatment response is strongly related to the neurocognitive status of the patient prior to initiation of treatment.41


CNS sarcoidosis may also present with dementia symptoms. It is a multisystem granulomatous disease that commonly affects the lungs, eyes and skin. The condition is difficult to diagnose but is responsive to steroids. With early treatment, reversal of symptoms may occur.36


Vascular Causative Factors


Dural arteriovenous fistulae (DAVF) have been associated with progressive cognitive dysfunction. These lesions often occur with focal neurological symptoms or signs, but cognitive impairment may be the sole manifestation.37


The prognosis after selective embolisation is very good, with complete resolution of the symptoms. Magnetic resonance angiography and catheter angiography show venous flow reversal and decreased perfusion of the cerebral parenchyma. Diagnosis is difficult, but DAVF should be in the differential diagnosis of atypical cases with subacute cognitive decline. It is hypothesised that the symptoms and imaging findings result from venous hypertension.


Infections


Infections of the CNS such as cryptococcal meningitis, Lyme disease, Whipple’s disease, syphilis and HIV could induce dementia symptoms. Early management of these infections may result in reversibility of the cognitive impairment. However, permanent damage and irreversibility of the cognitive symptoms is not an unusual scenario in untreated or undetected cases.


Whipple’s disease is very rare. The incidence is about 5–10 cases in one million every year. It can affect the CNS and present as dementia without gut involvement. It is difficult to diagnose, but treatable if managed when symptoms first start.38


Lyme disease is another treatable infection that can affect the CNS and present as dementia.39


Cognitive symptoms are a late complication of neurosyphilis. Diagnosis is easy and based on the evaluation of serology for Treponema pallidum. Syphilis is a common complication in immunocompromised patients.40


stroke and seizures. Angiitis of the CNS may have a fluctuating course or a stepwise rapid deterioration that could be misleading. The diagnosis is confirmed by conventional angiography or brain biopsy and the recommended treatment is a combination of corticosteroids and immunosuppression. Relapses are not unusual.


Serological tests for Treponema


should be available in everyday clinical practice, as the incidence of the disease has risen in recent years due to people migrating from underdeveloped countries.


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