Cervical spine MRI in Hirayama-disease
In neutral neck position
Inferior cervical cord segmental atrophy
Segmental cord flattening
High signal in the anterior aspect of the lower cervical cord
Loss of cervical lordosis
Loss of attachment (LOA) between the posterior dural sac and subjacent lamina
In neck flexion
Anterior shifting of the posterior wall of the dural canal
Enlarged posterior epidural component
Thoracic extension of the inferior cervical posterior epidural component
Prominent posterior epidural flow voids
Asymmetrical cord flattening on axial imaging
Post contrast enhancement of epidural component (Sonwalkar et al. 2008)
11.3.1 Brachial Amyotrophic Diplegia (BAD)
The term brachial amyotrophic diplegia (BAD) has been used to describe a slowly progressive lower motor neuron disorder affecting proximal arm muscles. The wasted arms hang limply at the sides giving the person the appearance of “a man in a barrel.” Another moniker is the “flail arm syndrome”. In most cases there is no obvious cause but reports have implicated HIV or HTLV-1 infection. In one case an axial view of the cervical spinal cord showed high signal in the anterior horns of the gray matter. Sjögren syndrome was held responsible for one patient with BAD who improved with combination therapy that included prednisone, plasmapheresis, and IVIG.
11.3.2 Cervical Spondylotic Myelopathy
The clinical manifestations of cervical spondylotic myelopathy can rarely mimic ALS. Observations from the Irish and Scottish ALS Registers suggest that cervical spondylotic myelopathy is more likely to show slowly progressive wasting of the arms and hands plus spastic paraplegia. However, there have been few documented reports of visible fasciculation. Also, the rate of progression is slower than in ALS, and the condition may be more symmetric than in ALS. Key clinical features identified by the Irish and Scottish Registers that raised the possibility of cervical myelopathy included the presence of upper motor signs caudal to lower motor signs, early bladder involvement, the absence of bulbar involvement, presence of sensory symptoms and the relatively slow progression. Neuroimaging is helpful in making the diagnosis. However, some people over the age of 40 have spondylosis with cord compression and may even show high signal within the cord—but they are asymptomatic. Also, 5–10 % of people with documented ALS have had cervical decompressive operations without benefit.
Misdiagnosing ALS as cervical myelopathy is more common than the converse.
11.3.3 HIV-Associated ALS
Brachial diplegia has been reported in HIV-positive patients. In 2006, Verma and Berger raised doubts about possibility that HIV might cause ALS because HIV is not a neurotropic virus and because, in comparison with HIV-negative ALS patients, the reported HIV-infected patients were younger, the course of ALS was more rapid, had atypical features and, perhaps most important, the ALS improved in some of those treated with highly active antiretroviral therapy (HAART) for the HIV-infection. On the other hand, about half of the treated HIV-infected patients succumbed to ALS. They concluded that “the causal relationship remains uncertain.” Primary lateral sclerosis may also appear with HIV-infections, but is rare.
11.3.4 Other Causes of Reversible Motor Neuron Disease
Motor neuron diseases usually progress inexorably to death. However, cases of complete resolution of sporadic motor neuron diseases with upper and lower motor neuron signs have been reported. The underlying pathology is unclear and such cases are extremely rare: no spontaneous resolutions of ALS have been noted among over 1400 population-based cases collected by the Irish ALS Register over 16 years. West Nile virus infections can cause a reversible poliomyelitis that differs from the others in having a much more acute course. Electrical injury, HTLV-1 infection, and lead intoxication can also cause reversible motor neuron syndromes.
11.4 Reversible Causes of Cognitive Decline
11.4.1 Delirium
This term implies an “acute impairment of cognition with a fluctuating course,” including a change in the level of consciousness. Impaired cognition, the acute and transient course, and also the many evident causes of delirium including metabolic, infectious and toxic, differentiate this cerebral dysfunction from both neurodegeneration and from dementia.
11.4.2 Mild Cognitive Impairment
Alzheimer disease (AD) classically presents with both subjective and caregiver reports of memory dysfunction which is sub-acute in onset but progressive. The condition tends to evolve with the pathological recruitment of other networks including dorsolateral prefrontal cortex causing executive dysfunction and language networks causing word finding problems. In clinical practice, most physicians deal regularly with patients with subjective complaints in any or all these domains, the majority of whom do not have a neurodegenerative disorder. In many cases, depression, anxiety or psychosocial stress can play a significant role. The lack of objective concern in family and caregivers, and the performance on standardized delayed word recall testing are usually enough to reassure. Nevertheless, there are some patients with mild subjective symptoms, without any negative effective on work or social performance who score poorly on testing and may have what we call “mild cognitive impairment” (MCI). This condition is believed to be in excess of what might be expected with normal aging and is a risk factor for the development of clinical dementia. The exact risk is unclear but about 80 % of MCI patients progress eventually to AD (see also Chap. 4). The remaining 20 % either remain stable or may even improve, two features that point towards a mimic syndrome rather than a neurodegenerative one. The mechanisms underpinning stable or improving MCI are unclear.
11.4.3 Drug Induced Encephalopathy
Medications are listed as the most common cause of reversible “dementia” but some drug effects must also include obtundation in addition to cognitive decline. That would be defined as delirium rather than dementia. Common causal drugs include anticholinergics, tricyclic antidepressants, opiate analgesia, antipsychotics, bismuth (in the form of bismuth subsalicylate, available as an over-the-counter medication), bromides, digoxin, antihistamines, antiepileptics, dopamine antagonist antiemetics, and lithium (See Table 11.2).
Table 11.2
Common drugs that can cause cognitive impairment
Drug | Effect |
|---|---|
Amitriptyline | Anticholinergic properties: Sedation, confusion, delirium, or hallucinations |
Anticholinergics | Sedation, confusion, delirium, or hallucinations |
Anticonvulsants valproate, levetiracetam | Confusion, sedation, elevated ammonia Confusion, hallucinations |
Antihistamines | Anticholinergic properties: sedation, confusion, delirium, or hallucinations |
Antipsychotics | Confusion, sedation |
Antispasmodics (GI) | Anticholinergic properties : Confusion, delirium, or hallucinations |
Baclofen | Hallucinations, impaired memory, catatonia, mania |
Barbiturates | Drowsiness, lethargy, depression, severe CNS depression |
Long-acting benzodiazepines | Sedation, drowsiness, ataxia, fatigue, confusion, weakness, dizziness, vertigo, syncope, psychological changes |
Bismuth subsalicylate | Encephalopathy resembling dementia. Encephalopathy resembling CJD |
Chlorpropamide | Hypoglycemia, which can result in altered mental state (confusion, amnesia, coma) |
Digitalis | Headache, fatigue, malaise, drowsiness, and depression |
H2 Receptor Antagonists | Confusion, hallucinations, agitation |
Indomethacin | Headache, dizziness, vertigo, somnolence, depression, fatigue |
Lithium | Confusion, sedation, movement disorder |
Methyldopa | May exacerbate depression |
Muscle Relaxants | Anticholinergic properties, weakness, confusion, delirium, or hallucinations |
Pentazocine | Confusion, hallucinations, dizziness, lightheadedness, euphoria, and sedation |
Reserpine | Depression, sedation |
The evaluation of a patient with cognitive impairment should therefore include a careful medication history, including a complete review of all over-the-counter medications.
11.4.4 Epilepsy
Non-convulsive status epilepticus or clusters of non-convulsive seizures may be focal onset or be part of a generalized epileptic syndrome. Occasionally, the only clinical manifestation may be altered mental status that appears more like delirium than dementia. Some patients, however, especially the elderly, may maintain such vigilance that the patient merely appears cognitively impaired. This has been called ‘epileptic pseudo-dementia’ a rare disorder that can be diagnosed only in the presence of unequivocal prolonged epileptiform discharges on the electroencephalogram (EEG) of the cognitively impaired patient. Treatment is that for other forms of non-convulsive status but as the term ‘epileptic pseudodementia’ implies a prolonged course, the prognosis for eventual recovery is poor.
11.4.5 Subdural Hematoma
Chronic subdural hematoma is the most frequent type of intracranial hemorrhage and may occur in the elderly following minor trauma. Patients may show a slow decline in cognitive function with confusion, impaired memory, headache and motor deficits or aphasia. Chronic subdural hematoma or hygroma should therefore be considered in the differential dementia of cognitive impairment. Diagnosis is by neuroimaging, and treatment is surgical evacuation.
11.4.6 Sleep Apnea
Sleep apnea can be associated with memory loss. Patients may present with symptoms suggestive on cognitive decline, and can account for up to 8 % of patients attending a young onset dementia clinic. Symptoms include daytime somnolence, snoring, and morning headache. The reversible cognitive decline is thought to relate to sleep deprivation and nocturnal hypoxemia. The diagnosis is established by overnight polysomnography with oxygen saturation monitoring. Treatment is with non invasive ventilation using a continuous positive air way pressure (CPAP) device.
11.4.7 Neuropsychiatric Conditions Associated with Reversible Cognitive Decline
11.4.7.1 Depression
Depressive pseudodementia has been defined as a reversible cognitive impairment of the type seen in dementia. It is associated with delusions and a history of affective illness.
There are few studies of the frequency of depressive pseudodementia, although rates as high as 18 % have been reported in specialist dementia referral centers.
Patients with cognitive impairment and concomitant depression should be treated aggressively with antidepressants and psychotherapy. However, clinically depressed patients with signs of pseudodementia are at higher risk of developing irreversible dementia in 2 or more years. This suggests that depression with reversible cognitive impairment could be a prodromal phase for dementia rather than a risk factor, and that patients with depressive pseudodementia should be followed closely.
The prevalence of depression in people with Parkinson disease varies in different reports from 20 to 80 % and often starts before the motor signs appear (See also Chap. 5). This problem of diagnosis is compounded because some syndromes are common in both conditions: bradykinesia, bradyphrenia, sleep and autonomic disorders, anorexia and weight loss, apathy, and loss of libido. However, the fundamental signs of parkinsonism (include tremor, cogwheel rigidity, loss of dexterity, deterioration of handwriting, frequent falls or loss of postural control) are not seen in patients with depression.
Severe depression may also mimic a predominantly apathetic presentation of FTD; cognitive testing should help distinguish the two with dysexecutive features much more prominent in the dementia (see also Chap. 7).
11.4.7.2 Catatonia
This complex neuropsychiatric syndrome may be seen with either a primary psychiatric disorder or with a general medical condition. Catatonia may mimic other neurodegenerative conditions including, FTD and Parkinson disease (Table 11.3). The acute onset of catatonia, with alternating agitation, stupor, and dysautonomia may respond to high-dose lorazepam or electroconvulsive therapy.
Table 11.3
Abnormal signs in catatonia
Motor | Speech & language | Behavioral | Autonomic | Laboratory |
|---|---|---|---|---|
Akinesia Bradykinesia Parkinsonism Tremor Stupor Primitive Reflexes Upgoing Plantars Oculomotor signs Tics | Mutism Aphasia Palilalia | Agitation Impaired judgment Impaired insight | Hypertension Pyrexia Diaphoresis Insomnia Tachycardia | Leukocytosis Elevated creatine kinase (CPK) Abnormal EEG |
11.4.7.3 Conversion Disorder
Conversion disorder is characterized by loss or alteration of physical function that suggests a physical disorder, but that has a psychological basis. Although conversion disorder are more likely to occur in younger patients—onset is unusual after 35 years of age, symptoms can mimic neurodegenerative disease. Common psychogenic mimic symptoms include limb paralysis, diverse movement disorders, gait disturbances, blindness and deafness. The patient’s behavior seems inappropriately accepting of or indifferent to the serious physical symptoms.
The Diagnostic and Statistical Manual of Mental Disorders (DSM IV) lists six criteria that must be filled for the diagnosis of conversion disorder (Table 11.4). All neurological and medical causes must be excluded.
Table 11.4
DSM IV criteria for conversion disorder
Patient has one or more symptom affecting voluntary, motor or sensory function that suggests a neurological or medical condition. |
Psychological factors are associated with the symptom or deficit. |
Symptom or deficit is not intentionally produced, but is maintained by secondary gain. |
Symptom or deficit cannot be fully explained by a general medical condition, by direct effects of a substance, or as a culturally sanctioned behavior or experience. |
Symptom or deficit causes clinically significant distress or impairment in social, occupational or other important areas of functioning, or warrants medical explanation. |
Symptom or deficit is not limited to pain or sexual dysfunction, and is not better accounted for by another mental disorder. |
11.4.7.4 Late Onset Psychiatric Disease
Late onset psychiatric disease may mimic fronto-temporal dementia.
Of the three main clinical syndromes of FTD (See Chap. 7), the behavioral variant FTD (bv-FTD), is the one most likely to be confused with a mimic disorder, the others having a more characteristic language dysfunction (semantic dementia or progressive aphasia). Detailed neuropsychological testing is helpful in distinguishing organic disease from a late onset psychiatric disorder.
11.4.8 Nutritional Causes of Reversible Cognitive Decline
Nutritional causes of cognitive decline may be detected by clues in different systems.
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