eMedicine Specialties > Neurology > Behavioral Neurology and Dementia

Dementia in Motor Neuron Disease: Differential Diagnoses & Workup

Author: Joe Verghese, MD, MRCPI, Associate Professor, Department of Neurology, Albert Einstein College of Medicine
Contributor Information and Disclosures

Updated: Nov 1, 2006

Differential Diagnoses

Alzheimer Disease
Amyotrophic Lateral Sclerosis
Dementia With Lewy Bodies
Frontal and Temporal Lobe Dementia
Frontal Lobe Syndromes
Pick Disease

Other Problems to Be Considered

Vascular dementia
Dementia in Parkinson disease

Workup

Laboratory Studies

  • Obtain typical blood studies, thyroid function tests, vitamin B12 and folate levels, and Venereal Disease Research Laboratory test. Refer to Amyotrophic Lateral Sclerosis for a full listing of the MND workup.

Imaging Studies

  • Computed tomography (CT) scan may show mild, generalized cerebral atrophy or asymmetric frontotemporal atrophy.
  • Because of greater resolution than CT, MRI studies may reveal selective frontal and anterior temporal atrophy that cannot be appreciated on CT.
  • Single photon emission computed tomography imaging often demonstrates reduced blood flow in an asymmetric, frontotemporal pattern.
  • A recent study reported that glucose hypometabolism on PET imaging in patients with dementia associated with motor neuron disease affected only the frontal lobes, sparing the temporal lobes. This is in contrast to frontotemporal dementia where glucose hypometabolism is seen in both frontal lobes and temporal lobes. In Alzheimer disease, PET scans may reveal glucose hypometabolism in the parietal and temporal regions bilaterally.

Other Tests

  • Electroencephalogram can remain normal even in later stages of dementia, but often mild dysrhythmic slowing occurs that is sometimes asymmetric.
  • Electromyography may demonstrate widespread denervation in limb muscles. Early in the disease, especially in predominantly bulbar onset patients, findings may not fulfill the Lambert or El Escorial criteria for MND.

Histologic Findings

Early in the disease, FTD/MND preferentially affects frontal and temporal lobes, the hypoglossal nucleus, and spinal motor neurons. Later and terminal stages reveal histologic evidence of widespread cortical involvement. In the frontal and temporal lobes, microscopic changes include loss of pyramidal cells, spongiform neuropil change, and astrocytic gliosis. Ubiquinated, tau-negative inclusions are present within the frontal cortex and the dentate gyrus of the hippocampus. Pick cells (inflated neurons) and Pick bodies (ubiquitin and tau-positive intracellular inclusions) are absent. Betz cells in the precentral gyrus usually are affected.

In approximately 50% of patients, neuronal loss and pigmentary incontinence in the substantia nigra and other pigmented brainstem neurons occurs, even in patients without clinically overt parkinsonism. There can be marked hypoglossal and spinal motor neuron degeneration (although this is not essential for patients to progress to an anarthric state) and ubiquinated tau-negative inclusions in the spinal neurons.

More on Dementia in Motor Neuron Disease

Overview: Dementia in Motor Neuron Disease
Differential Diagnoses & Workup: Dementia in Motor Neuron Disease
Treatment & Medication: Dementia in Motor Neuron Disease
Follow-up: Dementia in Motor Neuron Disease
References
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References

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  2. Gustafson L. Frontal lobe degeneration of non-Alzheimer type. II. Clinical picture and differential diagnosis. Arch Gerontol Geriatr. Sep 1987;6(3):209-23. [Medline].

  3. Hudson AJ. Amyotrophic lateral sclerosis and its association with dementia, parkinsonism and other neurological disorders: a review. Brain. Jun 1981;104(2):217-47. [Medline].

  4. Jeong Y, Park KC, Cho SS, et al. Pattern of glucose hypometabolism in frontotemporal dementia with motor neuron disease. Neurology. Feb 22 2005;64(4):734-6. [Medline].

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  6. Mitsuyama Y. Presenile dementia with motor neuron disease in Japan: clinico-pathological review of 26 cases. J Neurol Neurosurg Psychiatry. Sep 1984;47(9):953-9. [Medline].

  7. Neary D, Snowden JS, Mann DMA, et al. Frontal lobe dementia and motor neuron disease. J Neurol Neurosurg Psychiatry. 1990;53:23-32. [Medline].

  8. Neary D, Snowden JS, Mann DMA. The clinical pathological correlates of lobar atrophy. Dementia. 1993;4:154-159. [Medline].

  9. Neary D, Snowden J. Fronto-temporal dementia: nosology, neuropsychology, and neuropathology. Brain Cogn. Jul 1996;31(2):176-87. [Medline].

  10. Neary D, Snowden JS, Gustafson L, et al. Frontotemporal lobar degeneration: a consensus on clinical diagnostic criteria. Neurology. 1998;51:1546-54. [Medline].

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Further Reading

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Keywords

ALS dementia, frontotemporal dementia with motor neuron disease, FTD/MND, frontal lobe dementia with motor neuron disease, FLD/MND, MND, FTD

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Contributor Information and Disclosures

Author

Joe Verghese, MD, MRCPI, Associate Professor, Department of Neurology, Albert Einstein College of Medicine
Joe Verghese, MD, MRCPI is a member of the following medical societies: American Academy of Neurology and American Geriatrics Society
Disclosure: Nothing to disclose.

Medical Editor

Rodrigo O Kuljis, MD, Esther Lichtenstein Professor of Psychiatry and Neurology, Director, Division of Cognitive and Behavioral Neurology, Department of Neurology, University of Miami School of Medicine
Rodrigo O Kuljis, MD is a member of the following medical societies: American Academy of Neurology and Society for Neuroscience
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Richard J Caselli, MD, Professor, Department of Neurology, Mayo Medical School, Rochester, MN; Chair, Department of Neurology, Mayo Clinic of Scottsdale
Richard J Caselli, MD is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, American Medical Association, American Neurological Association, and Sigma Xi
Disclosure: Nothing to disclose.

CME Editor

Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.

Chief Editor

Howard A Crystal, MD, Professor, Departments of Neurology and Pathology, State University of New York Downstate; Consulting Staff, Department of Neurology, University Hospital and Kings County Hospital Center
Howard A Crystal, MD is a member of the following medical societies: American Academy of Neurology and American Neurological Association
Disclosure: Pfizer Honoraria Speaking and teaching; Myriad Honoraria Consulting

 
 
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