CSF-oma Identification With Nuclear Medicine Shunt-o-Gram.

A nuclear medicine shunt-o-gram is used to evaluate ventriculoperitoneal shunt patency and dispersion of radiotracer into the peritoneal cavity. A 73-year-old man presented with worsening memory, gait disturbance, and urinary incontinence. Shunt-o-gram revealed antegrade flow through the tubing and spillage into the peritoneal cavity without dispersion. CT confirmed a CSF-oma. Symptoms resolved after CSF-oma resection. Normal passage of radiotracer through the shunt without normal dispersion into the peritoneal cavity along with CT imaging correctly identified a CSF-oma. This is an unexpected complication of a shunt. Correct diagnosis on imaging likely saved this patient from unnecessary complete shunt revision.

Occipital and Cingulate Hypometabolism are Significantly Under-Reported on 18-Fluorodeoxyglucose Positron Emission Tomography Scans of Patients with Lewy Body Dementia.

OBJECTIVE: To determine whether occipital and cingulate hypometabolism is being under-reported or missed on 18-fluorodeoxyglucose positron emission tomography (FDG-PET) CT scans in patients with Dementia with Lewy Bodies (DLB). BACKGROUND: Recent studies have reported higher sensitivity and specificity for occipital and cingulate hypometabolism on FDG-PET of DLB patients. METHODS: This retrospective chart review looked at regions of interest (ROI's) in FDG-PET CT scan reports in 35 consecutive patients with a clinical diagnosis of probable, possible, or definite DLB as defined by the latest DLB Consortium Report. ROI's consisting of glucose hypometabolism in frontal, parietal, temporal, occipital, and cingulate areas were tabulated and charted separately by the authors from the reports. A blinded Nuclear medicine physician read the images independently and marked ROI's separately. A Cohen's Kappa coefficient statistic was calculated to determine agreement between the reports and the blinded reads. RESULTS: On the radiology reports, 25.71% and 17.14% of patients reported occipital and cingulate hypometabolism respectively. Independent reads demonstrated significant disagreement with the proportion of occipital and cingulate hypometabolism being reported on initial reads: 91.43% and 85.71% respectively. Cohen's Kappa statistic determinations demonstrated significant agreement only with parietal hypometabolism (p<0.05). CONCLUSION: Occipital and cingulate hypometabolism is under-reported and missed frequently on clinical interpretations of FDG-PET scans of patients with DLB, but the frequency of hypometabolism is even higher than previously reported. Further studies with more statistical power and receiver operating characteristic analyses are needed to delineate the sensitivity and specificity of these in vivo biomarkers.

Absent Cerebellar Circulation With Intact Cerebral Blood Flow on a 99mTc Bicisate "Brain Death" Study.

A 55-year old woman presented in an obtunded state and was found to have a subarachnoid hemorrhage. After endovascular repair, her condition deteriorated, and brain death was suspected. A Tc bicisate brain blood flow study was performed, which showed a complete absence of blood flow to the cerebellum despite intact circulation to the cerebral hemispheres. These atypical findings are likely a result of a transient intracranial pressure differential and the timing of the study. A timely and accurate declaration of brain death has important psychosocial and ethical implications, particularly when organ donation is being considered.

Association between an Alzheimer's Disease-Related Index and APOE ε4 Gene Dose.

BACKGROUND: We introduced a hypometabolic convergence index (HCI) to characterize in a single measurement the extent to which a person's fluorodeoxyglucose positron emission tomogram (FDG PET) corresponds to that in Alzheimer's disease (AD). Apolipoprotein E ε4 (APOE ε4) gene dose is associated with three levels of risk for late-onset AD. We explored the association between gene dose and HCI in cognitively normal ε4 homozygotes, heterozygotes, and non-carriers. METHODS: An algorithm was used to characterize and compare AD-related HCIs in cognitively normal individuals, including 36 ε4 homozygotes, 46 heterozygotes, and 78 non-carriers. RESULTS: These three groups differed significantly in their HCIs (ANOVA, p = 0.004), and there was a significant association between HCIs and gene dose (linear trend, p = 0.001). CONCLUSIONS: The HCI is associated with three levels of genetic risk for late-onset AD. This supports the possibility of using a single FDG PET measurement to help in the preclinical detection and tracking of AD.

Thyroid stimulating hormone and cognition during severe, transient hypothyroidism.

OBJECTIVE: The purpose of our pilot study was to explore the relationship between serum thyroid stimulating hormone (TSH) levels during overt hypothyroidism (OH) and hypothyroid-related neuropsychological symptoms. We hypothesized that TSH level may reflect the degree of 'brain hypothyroidism' such that an inverse correlation may exist between serum TSH and cognitive function in patients experiencing overt hypothyroidism (OH), and sought to explore this hypothesis. METHODS: Eleven thyroidectomized patients underwent neuropsychological and thyroid function testing while overtly hypothyroid, and again following thyroid hormone replacement. Their test performance was compared with that of eleven healthy controls at a similarly separated two points in time, and the change over time for the patient group and the controls was likewise assessed and compared. The patients' neuropsychological test scores were then correlated with their serum TSH levels while hypothyroid. RESULTS: The patients' performance while hypothyroid was worse than that of the controls in only one neurocognitive measure--Working Memory Index. The subjects improved similarly or to a greater degree than the controls, when the subjects were thyroid hormone replaced, on all but one neurocognitive measure - Thurstone Word Fluency. TSH level during hypothyroidism was inversely proportional to the patients' performance on these same two measures, but no others. CONCLUSION: Serum TSH level during hypothyroidism was inversely proportional to performance on the only two neurocognitive measures evidencing an adverse effect from hypothyroidism in our cohort. This suggests that serum TSH level may reflect the severity of 'brain hypothyroidism' during the overt stage of this condition.

Technetium-99m ethyl cysteinate dimer (ECD) cerebral accumulation and symptom and sign severity during hypothyroidism.

OBJECTIVE: The purpose of this study was to correlate hypothyroid-related symptomatology with regional cerebral blood flow (rCBF) during hypothyroidism. MATERIALS AND METHODS: Nine thyroidectomized patients underwent neuropsychological testing and single photon emission computed tomography (SPECT) of their brains with technetium-99m (Tc-99m) ethyl cysteinate dimer (ECD), a lipophilic cerebral blood flow radiotracer, while hypothyroid, and again following thyroid hormone replacement. Neuropsychological test scores and TSH levels while hypothyroid were correlated with rCBF in hypothyroid-affected areas of the brain. RESULTS: Correlations were found during hypothyroidism between the noted parameters and ECD radiotracer accumulation in the following respective regions, all of which demonstrated hypothyroid-related cerebral blood flow (CBF) aberrations: TSH and left middle occipital gyrus; psychomotor performance speed and left precentral gyrus; and depression and right middle frontal gyrus, left middle frontal gyrus, right insula, and left thalamus. CONCLUSIONS: Severity of psychomotor impairment and depression, and TSH level during hypothyroidism appeared to correlate with CBF to brain regions associated with motor activity, mood and vision, respectively; and previously shown to manifest significantly altered rCBF during hypothyroidism.

Symptomatic hyponatremia in association with a low-iodine diet and levothyroxine withdrawal prior to I131 in patients with metastatic thyroid carcinoma.

BACKGROUND: Strategies to improve I131 uptake in thyroid carcinoma include levothyroxine (LT4) withdrawal or thyrotropin (TSH) administration along with a low-iodine diet. We report five patients with papillary or follicular thyroid carcinoma who developed symptomatic hyponatremia during LT4 withdrawal and low-iodine diet. RESULTS: Four patients had pulmonary and/or brain metastases. All had restricted iodine intakes during LT4 withdrawal. Presenting complaints included weakness, dizziness, fainting spells, lethargy, and/or nausea. Baseline serum sodium levels while on LT4 suppression were normal. During presentation all were hypothyroid and serum sodium ranged from 110 to 121 mmol/L (normal 135-148). Despite hyponatremia, the plasma renin activity and serum aldosterone levels were suppressed, indicating volume expansion. The hyponatremia responded to fluid restriction and normalized after LT4 replacement. Low sodium intake, inappropriate antidiuretic hormone secretion syndrome (SIADH)-like disorder secondary to hypothyroidism and/or lung or cerebral metastases may have contributed to hyponatremia. CONCLUSIONS: The development of hyponatremia during LT4 withdrawal and low-iodine diet in otherwise healthy patients with thyroid carcinoma is extremely rare. However, elderly patients with metastatic thyroid carcinoma need observation during LT4 withdrawal combined with a low-iodine diet and should receive instruction to take iodine-free sodium chloride. Free water restriction may be necessary in some patients.

Exercise-related longitudinal tibial stress fracture in a young person.

A 22-year-old man presented to the Nuclear Medicine Clinic for evaluation of distal right tibial pain. The patient reported recently beginning a rigorous exercise program involving lower extremity impact temporally related to the onset and worsening of the pain. The physical examination was remarkable for significant tenderness to palpation of the distal one-third of his right tibia. The presumptive diagnosis was a stress fracture. Recent roentgenograms of the right tibia were not available for review but were reportedly normal. Scintigraphy, in combination with computed tomography, revealed an unusual type of stress fracture (particularly in a young person and in relation to exercise)--a longitudinal stress fracture.

Cerebral accumulation of Tc-99m ethyl cysteinate dimer (ECD) in severe, transient hypothyroidism.

Thyroid dysfunction is a well-known contributor to psychiatric morbidity. To investigate the mechanism(s) by which thyroid hormone availability affects cerebral activity, a group of thyroidectomized individuals were studied at two points in time: when markedly hypothyroid in preparation for a thyroid cancer metastatic survey and when clinically and/or biochemically euthyroid. The analysis consisted of single photon emission computed tomography (SPECT) using a lipophilic radiopharmaceutical, technetium-99m (Tc-99m) ethyl cysteinate dimer (ECD), and measurement of mood, anxiety, and psychomotor function, at both points in time. Both increases and decreases in regional cerebral radiotracer activity were found in the hypothyroid condition relative to the euthyroid condition, and the neuropsychological assessment demonstrated significantly greater depression, anxiety, and psychomotor slowing during the hypothyroid state. Increased radiotracer activity was seen in frontal and temporal regions, posterior cingulate gyrus, thalamus, and putamen. Decreased activity was seen in the occipital cortex, and the pre- and postcentral gyri. This distribution pattern is partially consistent with findings in persons with depression and anxiety unrelated to thyroid disease, supporting the link between the symptoms observed in our subjects and their marked hypothyroidism. Finally, these results support the need to consider the effect of the thyroid state on cellular mechanisms of uptake and retention of cerebral blood flow radiopharmaceuticals when studying 'noneuthyroid' individuals.

Presentation of gastric carcinoma on a radionuclide gastric-emptying study.

We present a case of unsuspected gastric carcinoma discovered as a result of abnormalities seen on a sulfur colloid gastric-emptying study. Considered a functional or physiological analysis, often relatively little attention is given to the morphology of the stomach except for the purpose of drawing a region of interest. This case, in which the images suggested a space-occupying lesion(s), emphasizes the importance of careful examination for "pathoanatomy" as well as pathophysiology in functional imaging.