Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (95 page)

   Laboratory Findings

Laboratory testing to determine the causative disease or toxin should be based on the presenting symptoms and history of the patient to rule out the preceding disorders. All patients with diabetes should be screened for autonomic neuropathy with a complete history and physical examination, including evaluation of heart rate, respiratory rate, response to the Valsalva maneuver, and evaluation for orthostatic hypertension.

References

1.  Boulton AJ, Vinik AI, Arezzo JC, et al. Diabetic neuropathies: a statement by the American Diabetes Association.
Diabetes Care.
2005;28:956.

2.  Freeman R. Autonomic dysfunction. In: Samuels M, Fesky S, eds.
The Office Practice of Neurology
, 2nd ed. Philadelphia, PA: Churchill Livingstone; 2003;14:141–145.

PSEUDOTUMOR CEREBRI

   Definition

Pseudotumor cerebri is idiopathic intracranial hypertension.

   Clinical Presentation

Patients present with headache and papilledema. The CSF is normal except for increased opening pressure. The primary means of diagnosis is one of exclusion and consists of neuroimaging to rule out a mass lesion or ventricular obstruction, funduscopic exam to rule out papilledema, and visual field testing to determine the severity of optic nerve involvement.
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   Laboratory Findings

Laboratory findings may help in the diagnosis of “secondary pseudotumor cerebri,” which is due to an underlying condition. Lumbar puncture should be performed only after neuroimaging to measure the opening pressure and to evaluate for cell count, differential, and glucose and protein levels. Culture and cytology may be indicated based on the clinical situation. Obesity has been associated with increased CSF opening pressures.
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Testing may be helpful to rule out Addison disease, infection, and metabolic disorders including acute hypocalcemia and other electrolyte disturbances, empty sella syndrome, and pregnancy. Testing for drugs that may be implicated in secondary pseudotumor cerebri includes psychotherapeutic drugs, sex hormones and oral contraceptives, and a reduction in dosage of corticosteroids. Immune diseases may be implicated, including SLE, polyarteritis nodosa, and serum sickness. Other conditions that may be tested for as the symptoms warrant include sarcoidosis, Guillain-Barré syndrome, head trauma, various anemias, and chronic renal failure.

References

1.  Friedman DI, Jacobson DM. Diagnostic criteria for idiopathic intracranial hypertension.
Neurology.
2002;59:1492.

2.  Corbett JJ, Mehta MP. Cerebrospinal fluid pressure in normal obese subjects and patients with pseudotumor cerebri.
Neurology.
1983;33:1386.

DISORDERS OF MOVEMENT

PARKINSON DISEASE

   Definition

Parkinson disease (PD) is a progressive neurodegenerative disorder resulting from the loss of dopaminergic cells in the substantia nigra.

   Clinical Presentation

Patients present with rest tremor, rigidity, bradykinesia, and gait disturbance. In the late stages, PD may result in dementia (see Dementia). The differential diagnosis includes essential tremor, dementia with Lewy bodies, cortical basal degeneration, progressive supranuclear palsy, and multiple system atrophy. It must also be distinguished from secondary parkinsonism due to drugs, toxins, head trauma, infections, cerebrovascular disease, and metabolic disorders.
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The diagnosis is based on clinical evaluation, there are no specific physiologic or blood tests to confirm the diagnosis. Neuroimaging is usually not helpful in distinguishing PD from other syndromes with motor disorders. MRI may be performed to exclude structural abnormalities of the brain. Olfactory dysfunction is seen early in PD, and testing may help to establish the diagnosis.
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At autopsy, gross sectioning of the brain stem through the substantia nigra reveals the loss of pigmentation. Microscopy demonstrates loss of neurons and Lewy Bodies (see eBook Figures 4-7 and 4-16).

References

1.  Tolosa E, Wenning G, Poewe W. The diagnosis of Parkinson’s disease.
Lancet Neurol.
2006;5:75.

2.  Katzenschlager R, Zijlmans J, Evans A, et al. Olfactory function distinguishes vascular parkinsonism from Parkinson’s disease.
J Neurol Neurosurg Psychiatry.
2004;75:1749.

PROGRESSIVE SUPRANUCLEAR PALSY

   Definition

Progressive supranuclear palsy (PSP) is a neurodegenerative disorder resulting in the loss of neurons and glia in the basal ganglia, brain stem, cerebral cortex, dentate nucleus, and upper spinal cord.

   Clinical Presentation