Dementia Reversal in Post-shunt Normal Pressure Hydrocephalus Predicted by Neuropsychological Assessment

        Journal of The American Geriatric Society,
May, 2001; Volume 49, pp 685=686


To the Editor: Eight cases (ages: M=65, 74, 78, 80, 81, 83/F=72, 76) are reported of geriatric normal pressure hydrocephalus (NPH) identified over a three-year period using neuropsychological assessment (NPA;M.G.) and neurosurgically (W.J.M.) treated with ventriculoperitoneal shunting. These cases were admitted by primary care physicians for Alzheimer's rule out/mental status change workup at a community hospital on the geriatric service where a behavioral medicine/neuropsychologist (M.G.) attended daily medical rounds.

Metabolic, hematologic and comprehensive laboratory studies including RPR, hair analyses for heavy metals, and toxicology screening were all negative. No contributing polypharmacy issues were identified. Although a previous report using NPA demonstrated "normal" serum vitamin B12 levels (250-450 pg/ml) were associated with reversible B12 deficiency dementia symptoms1, these eight patients had serum B12 levels above 500 pg/ml. All eight patients were medically stable. None had obvious focal neurologic cranial nerves II-XII deficits, and no patient had any history of hypoxemia.

Initial NPA screening found these eight patients to have intact frontal lobe/executive functioning/mental abstraction abilities, which are typically inconsistent with Alzheimer's dementia. However, the symptom triad of gait disturbance, urinary incontinence, and dementia/cognitive impairment was observed in all eight. An extensive bedside NPA revealed moderately impaired visuo-constructional reproduction/memory abilities with significant micrographia in all eight patients. Neither ideomotor apraxia nor visuospatial memory deficits were found. Auditory/verbal immediate and delayed recall memory were grossly intact. Remote-remote memory was preserved for chronologies and facts. This group was also found to display moderate cognitive slowing (bradyphrenia) with intact receptive and expressive speech. Other clinical signs were also positive including Parkinson-like fine motor hand tremors at rest, flat affect, "masked facies", bradykinesia, mild elbow cogwheeling rigidity, low voice tone and previously noted micrographia history for their signatures. Of utmost differential diagnostic value, however, is that six of eight patients had severely impaired bilateral tactile memory without stereoagnosia on initial non-visual, tactile only identification; while two patients (74- and 83-year-old males) had grossly intact tactile memory, also without stereoagnosia on initial non-visual tactile only identification.
Amantadine 100 mg BID was initiated in all eight patients which moderately controlled tremor and improved bradykinesia and mood, but had no effect on the severely impaired bilateral tactile memory found in six of these eight patients. Visuo-constructional memory, bradyphrenia, micrographia, gait, and incontinence remained unchanged by Amantadine in all eight patients. Due to an overall lack of response to Amantadine, the Parkinson-like signs/symptoms occasionally observed in NPH2,3, and the sub-cortical rather than cortical NPA deficit pattern, a neurosurgical consult was requested. The CT and MRI radiologic studies showed age-related ventriculomegaly without lesions. Positive cisternograms obtained over 72 hours documented abnormal, delayed patterns of CSF dynamics in all eight patients.

All eight patients ultimately received neurosurgical placement of ventriculoperitoneal shunts. Repeat bedside follow-up NPA now revealed grossly intact bilateral tactile memory in all eight patients. Noteworthy is that only in the pre-operative sub-group of those six patients with severely impaired bilateral tactile memory did visuo-constructional reproduction/memory improve from moderately impaired (16th percentile) pre-operatively to mildly impaired postoperatively (25th to 37th percentile). Also complete disappearance of bradyphrenia, bradykinesia, micrographia, and other aforementioned Parkinson-like signs/symptoms occurred despite discontinuing Amantadine pharmacotherapy the day of surgery. Additionally, gait improved greatly and urinary incontinence moderately improved except in one male with a prior prostatectomy history. Again, these improvements were found only in the six patients with severely impaired preoperative tactile memory. The two post-shunt patients (74- and 83-year-old males) without preoperative severely impaired tactile memory never demonstrated any significant neurologic nor objective NPA improvement of their dementia/cognitive functioning despite positive pre-operative cisternograms.

DISCUSSION

A major factor limiting NPH shunt success is the poor rate of significant dementia reversal found only in approximately 26% of neurosurgically shunted patients4,5,6,7. Patient selection criteria remain controversial. Previous investigations4,7 have attempted to respond to a call8, p.591 to find NPA predictors for post-shunt NPH dementia reversal. However, they did not utilize NPA/behavioral neurology measures neuroanatomically more sensitive to the symptoms of sub-cortical deficits, perhaps related to compression or stretching from ventriculomegaly or parenchymal pathology changes.
Thus, NPA of tactile memory may represent a heretofore-new non-invasive, economical technique, which may improve diagnostic accuracy by helping to identify patients with a reversible dementia due to NPH from other non-reversible dementias. Therefore, neuropsychological diagnostic testing sensitive to sub-cortical dysfunctions may improve neurosurgical selection criteria and ultimate dementia reversal of suspected NPH patients.

Mark Goodman, Ph.D., M.A.
Clinical Assistant Professor; UMDNJ-SOM
West Orange, New Jersey, U.S.A.

William J. Meyer, Ph.D., M.D. 
Bakersfield, California, U.S.A. 

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