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Clinical findings and diagnostic tests in the MV2 subtype of sporadic CJD

Anna Krasnianski, Walter J. Schulz-Schaeffer, Kai Kallenberg, Bettina Meissner, Donald A. Collie, Sigrun Roeber, Mario Bartl, Uta Heinemann, Daniela Varges, Hans A. Kretzschmar, Inga Zerr
DOI: http://dx.doi.org/10.1093/brain/awl123 2288-2296 First published online: 23 May 2006

Summary

Atypical clinical course and low sensitivity of established diagnostic tests are the main diagnostic problems in the MV2 subtype of sporadic Creutzfeldt–Jakob disease (sCJD). Clinical symptoms and signs, MRI, EEG and biochemical CSF markers were studied in 26 patients. Histological findings were semiquantitatively evaluated. Compared with typical sCJD, the disease duration was prolonged (median 12 months). Dementia, ataxia and psychiatric symptoms were present in all patients. Extrapyramidal signs were observed in 88%. T2-weighted MRI showed basal ganglia hyperintensities in 90%. Increased thalamic signal intensity was detected in 88% on diffusion-weighted MRI. Increased CSF tau-protein was found in 83%, and the 14-3-3 test was positive in 76%. The EEG revealed periodic sharp wave complexes in only two patients. Kuru plaques, severe thalamic and basal ganglia gliosis and spongiform changes, and neuronal loss in the pulvinar were the prominent histological features. At least one of the three diagnostic tests (MRI, tau- and 14-3-3 protein) supported the clinical diagnosis in all patients. MRI was the most sensitive of the diagnostic tests applied. Thalamic hyperintensities were observed unusually frequently. Prolonged disease duration, early and prominent psychiatric symptoms, absence of typical EEG, thalamic hyperintensities on MRI and relatively low 14-3-3 protein sensitivity may be suspicious for variant CJD. However, distinct sensory symptoms and young age at onset, which are often found in the latter, are not common in the MV2 subtype, and the pulvinar sign was observed in only one case.

  • CJD
  • MV2 subtype
  • MRI
  • Pulvinar sign
  • diagnosis

Introduction

Sporadic Creutzfeldt–Jakob disease (sCJD) is a rare transmissible disease characterized by accumulation of pathological prion protein (PrPSc) in the CNS. The polymorphism at codon 129 of the prion protein gene (PRNP) and the prion protein types 1 and 2 are the basis for a molecular classification of sCJD (Parchi et al., 1996, 1999). An alternative classification of sCJD included the polymorphism at codon 129 and three main prion protein types (Collinge et al., 1996; Hill et al., 2003).

The most common MM1/MV1 sCJD subtype is found in 75% of sCJD cases (Parchi et al., 1999). According to them the MV2 subtype comprises 9% of sCJD cases. Ataxia, dementia, the lack of PSWCs and prolonged disease duration were reported as typical in the MV2 subtype. Kuru plaques were the most characteristic histological finding. However, neither MRI nor biochemical CSF analysis was performed in that study. In other studies on a limited number of MV2 patients, a low sensitivity of the 14-3-3 protein test was reported (Zerr et al., 2000b; Castellani et al., 2004).

Atypical clinical course and low sensitivity of established diagnostic tests have been reported to be the main problems for diagnosing the MV2 subtype. The aim of the present study is to improve the diagnosis of patients with this sCJD subtype. We performed a detailed analysis of clinical features, EEG and MRI in 26 patients with the MV2-type sCJD. Biochemical CSF markers such as tau-protein, neuron-specific enolase (NSE), S-100B and Aβ-peptide 1-42 were investigated in addition to 14-3-3 proteins.

Patients and methods

Study design

German patients with suspected CJD were reported to the CJD Surveillance Unit in Göttingen and Munich and examined on site. CSF, blood samples and copies of the important diagnostic tests (MRI, EEG, laboratory tests) were taken. The patients were classified according to established diagnostic criteria (WHO, 1998, 2001; Zerr et al., 2000a).

MRI and EEG findings

The MR images from MV2 patients and, additionally, from control patients with the MM1 subtype were reviewed by two neuroradiologists (K.K. and D.C.) who were aware of the clinical diagnosis, but not of the CJD type (sporadic, familial, iatrogenic, variant CJD), codon 129 genotype, PrPSc type or clinical features. Seven cortical regions, the basal ganglia and cerebellum were analysed semiquantitatively for hyperintensities in each available imaging. The EEGs were analysed according to established criteria (Steinhoff et al., 1996).

Neuropathological and molecular studies

From 1993 to 2004, 582 neuropathologically confirmed sCJD cases were identified in Germany. The PrPSc type was determined in 221 of them according to Parchi et al. (1996). Western blot analysis, immunohistochemistry and the analysis of PRNP were performed by standard methods (Kitamoto et al., 1992; Kretzschmar et al., 1996; Schulz-Schaeffer et al., 2000). No PRNP mutations were detected. Semiquantitative evaluation of spongiosis, neuronal loss and gliosis was performed as described previously (Parchi et al., 1999). Eleven brain regions (superior frontal, cingulated, inferior temporal and inferior parietal gyrus; visual cortex; head of the caudate nucleus; middle part of the putamen; the pulvinar and dorsomedial thalamic nucleus; CA1 region of hippocampus; and vermis of the cerebellum) were investigated.

Biochemical CSF analysis

The 14-3-3 protein analysis was performed at least twice in each CSF sample as described previously (Zerr et al., 1998). Tau-protein was measured by Innotest hTau ELISA, and Aβ-peptide 1-42 by Innotest β-Amyloid 1-42 ELISA (Innogenetics N.V., Ghent, Belgium). NSE and S-100B were quantified by a commercially available immunoluminometric assay (Liaison NSE and Liaison Sangtec 100, DiaSorin S.p.A. Saluggia, Italy).

Statistical analysis

Significances (P) were tested by the Sigmastat 3.1 software (Systat Software Inc., Point Richmond, USA) using the Student's t-test/Mann–Whitney rank sum test or chi-square test/Fisher exact test. Correlations (r) were tested by the Sigmastat 3.1 software using Pearson test. A P-value <0.05 was considered as statistically significant.

Results

Study collective

The MV heterozygosity at codon 129 of the PRNP and the PrPSc type 2 were found in 26 patients (12% of 221 patients investigated; 15 female, 11 male). The median age at onset was 64 years (range 53–75); the median disease duration was 12 months (range 4–27).

Clinical findings

The data on the clinical symptoms and signs including the time of onset are shown in Tables 1, 2 and 3. Dementia (n = 10) and ataxia (n = 9) were the most common initial symptoms. Two patients presented with blurred vision; two with extrapyramidal tremor; and one each with paraesthesia, unspecified anxiety and nervousness. Dementia, ataxia and psychiatric symptoms were present in all patients, and extrapyramidal signs were observed in 88% during the disease course. In 18% the disease remained monosymptomatic for longer than 6 months. CJD was not suspected initially in any patient (Table 4), but for the first time 8 months after disease onset (mean).

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Table 1

Main symptoms and signs—time of onset (months) in 26 patients

Symptom/signMedianMean ± SDRange
Dementia11.9 ± 2.60–11
Ataxia12.1 ± 3.10–11
Extrapyramidal66.3 ± 4.20–15
Myoclonus7.58.4 ± 4.23–17
Visual/oculomotor7.56.8 ± 4.50–12
Pyramidal87.4 ± 3.43–13
Akinetic mutism9.59.0 ± 2.95–12
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Table 2

Clinical symptoms and signs during disease course in 26 patients

Symptoms and signsn (%)
Dementia26 (100)
Ataxia26 (100)
Extrapyramidal23 (88)
    Rigidity*19 (73)
    Tremor9 (34)
    Involuntary movements6 (23)
    Akinesia3 (11.5)
Myoclonus18 (69)
Visual/oculomotor12 (47)
    Gaze palsy3 (11.5)
    Saccadic pursuit3 (11.5)
    Nystagmus2 (8)
    Diplopia1 (4)
    Blurred vision1 (4)
    Metamorphopsia1 (4)
    Hemianopsia1 (4)
Pyramidal9 (34)
Akinetic mutism4 (15)
Vegetative9 (34)
    Loss of weight8 (31)
    Hyperhidrosis4 (15)
    Obstipation1 (4)
Other
    Primitive reflexes17 (65)
    Dysarthria15 (58)
    Sleep disturbance14 (54)
    Dizziness10 (38)
    Dysphagia7 (27)
    Vigilance disorder6 (23)
    Sensory5 (18)
    Epileptic seizures3 (12)
    Headache3 (12)
    Weight gain1 (4)
  • *Rigidity was considered as present if the tone increase was waxy or a cogwheel phenomenon was found.

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Table 3

Psychiatric and neuropsychological symptoms and signs in 26 patients during disease course

Symptoms and signsn (%)
Psychiatric26 (100)
    Hallucinations*13 (50)
    Restlessness11 (42)
    Depression10 (38)
    Fear10 (38)
    Aggressiveness9 (34)
    Paranoia7 (27)
    Euphoria3 (11.5)
Neuropsychological17 (65)
    Disorder of frontal brain17 (65)
    Apraxia12 (47)
    Aphasia9 (34)
    Acalculia2 (8)
    Agraphia2 (8)
    Spatial agnosia1 (4)
  • *Visual hallucinations in all patients with hallucinations; acoustic hallucinations in four of these patients.

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Table 4

Initial diagnosis in 26 patients

Diagnosisn
Multiple system atrophy5
Alzheimer's disease4
Unclassified dementia3
Dementia and ataxia3
Depression2
Psycho-organic syndrome1
Hysterical neurosis1
Somatization1
Pick's disease1
Dementia and polyneuropathy1
Tremor and polyneuropathy1
Unclear ataxia1
Delirium1
Unclear dementia and cervical myelopathy1

Magnetic resonance imaging

MR images were available in 20 patients. The investigation was performed in the median 8 months after symptom onset (range 1–18 months). The semiquantitative evaluation of the MRI findings is shown in Table 5. Basal ganglia hyperintensities on T2-weighted MRI were found in 90% of the patients. The highest sensitivity for cortical hyperintensities was observed in the DWI (88%) with the frontal cortex as the most commonly affected region (63%). Hyperintensities in the pulvinar (Fig. 1) were found in 5 of 20 patients (25%) on T2-weighted MRI and in 7 of 8 patients with available DW (88%). However, the classical pulvinar sign according to revised criteria was seen in only one patient on FLAIR and DWI imaging (Fig. 2) (Collie et al., 2001). The occurrence of thalamic hyperintensities showed no significant correlation with disease duration or time at which the MRI was performed.

Fig. 1

Axial PD-weighted MRI showing hockey stick-like thalamic hyperintensities. The pulvinar signal is not more intense than in other subcortical nuclei.

Fig. 2

(A) Axial FLAIR-weighted and (B) diffusion-weighted MRI showing the pulvinar sign.

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Table 5

Signal hyperintensities on MRI in 20 patients

T2 (n = 20)FLAIR (n = 10)PD (n = 7)DWI (n = 8)
Cortical4 (20%)8 (80%)3 (43%)7 (88%)
    Frontal2 (10%)4 (40%)2 (29%)5 (63%)
    Cingulate gyrus2 (10%)5 (50%)3 (43%)3 (38%)
    Parietal3 (15%)4 (40%)2 (29%)3 (38%)
    Occipital2 (10%)6 (60%)2 (29%)4 (50%)
    Hippocampus1 (5%)1 (13%)
    Temporal3 (15%)4 (40%)2 (29%)3 (38%)
    Insula2 (25%)
Basal ganglia18 (90%)10 (100%)7 (100%)8 (100%)
    Nucleus caudatus18 (90%)10 (100%)7 (100%)8 (100%)
    Putamen17 (85%)9 (90%)6 (86%)6 (75%)
    Pallidum2 (10%)1 (10%)
Pulvinar thalami5 (25%)7 (70%)4 (57%)7 (88%)
Cerebellum

Surprisingly high frequency of thalamic hyperintensities in our MV2 patients led us to compare their MRI findings with those of 17 German CJD study MM1 patients presenting the classical sCJD subtype (17 T2-, 10 FLAIR-, 6 DWI- and 4 PD-weighted MRI). Basal ganglia hyperintensities were found in 83% of DWI-, 70% of FLAIR-, 50% of PD- and 41% of T2-weighted MRI. No thalamic hyperintensities were detected in the MM1 patients.

EEG

The data on at least two EEGs (range 2–6; median 4 months) were available in all patients. The first EEG was obtained 4.5 months (median; range 0.5–15 months) and the last EEG 10 months (range 2.5–19 months) after disease onset. PSWCs were found in only two patients 4 months and 11.5 months after onset (sensitivity 8%).

CSF

A lumbar puncture (LP) was performed in 25 patients (once in 20, twice in 3, three times in 2 patients). Data on sensitivity of the biochemical markers and repeated LPs are shown in Table 6. Repetitive LPs led to detection of 14-3-3 proteins in two of three initially negative patients. The interval between the repeated LPs varied from 21 days to 9 months (median 3 months). The positive 14-3-3 test was obtained 8 months and the negative one 6 months after the disease onset (medians). The time at which the LP was performed was not significantly different in the two groups. The tau-protein was the most sensitive CSF marker (83%). The simultaneous tau- and 14-3-3 protein investigation showed the highest sensitivity (89%).

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Table 6

Biochemical CSF markers in MV2 patients

CSF markerRangeMedian1. LPSensitivity 1. LP (%)2. LP3. LPCumulative sensitivity (%)
14-3-3 protein17/25683/51/276
Tau (cut-off >1300 pg/ml)316–13 153 pg/ml2610 pg/ml17/24713/51/283
Aß 1-42 (cut-off <450 pg/ml)120–682 pg/ml366 pg/ml14/23614/40/170
S-100 B (cut-off >4.2 ng/ml)0.9–20.4 ng/ml4.9 ng/ml15/24634/41/167
NSE (cut-off >25 ng/ml)2–95 ng/ml30 ng/ml13/24543/52/263
  • 1. LP = first lumbar puncture; 2. LP = second lumbar puncture; 3. LP = third lumbar puncture. Number of patients with positive test as numerator; number of patients investigated as denominator.

About 25% of our MV2 patients could be classified either as possible sCJD or as possible vCJD and one patient as probable vCJD or probable sCJD according to WHO criteria (WHO, 1998, 2001; Will et al., 2000).

Histological findings

Semiquantitative analysis of gliosis, spongiform changes and neuronal loss was performed in 11 brain regions in 20 patients (Table 7). Spongiform changes were the most prominent histological finding except for the pulvinar and the vermis, where gliosis was the most distinct feature. The caudate nucleus showed the most pronounced spongiform changes, whereas gliosis and neuronal loss were especially prominent in the pulvinar. Nerve cell loss correlated significantly with disease duration in four cortical regions and in the pulvinar (r = 0.607; P = 0.0045 for temporal, r = 0.499; P = 0.0251 for occipital, r = 0.576; P = 0.0098 for parietal, r = 0.722; P = 0.0003 for frontal cortex; r = 0.569; P = 0.03 for the pulvinar). Gliosis correlated significantly with disease duration in three cortical regions (r = 0.524; P = 0.0177 for temporal, r = 0.531; P = 0.0192 for parietal, r = 0.575; P = 0.0079 for frontal cortex). Spongiform changes correlated significantly with disease duration only in the frontal cortex (r = 0.609; P = 0.0043). No significant difference was found in the severity of histological changes in the pulvinar in patients with or without the positive pulvinar sign on MRI. In the cerebellum, kuru plaques were seen in all patients.

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Table 7

Semiquantitative analysis of neuropathological changes in MV2 patients

ThalamusBasal gangliaCortexHippocampusCerebellum
Pulvinar (n = 14)Mediodorsal nucleus (n = 16)Putamen (n = 19)Caudate nucleus (n = 19)Frontal (n = 20)Cingulate gyrus (n = 20)Parietal (n = 19)Occipital (n = 20)Temporal (n = 20)CA1 region (n = 20)Vermis (n = 20)
Gliosis3.0 ± 0.52.8 ± 0.62.3 ± 0.72.5 ± 0.72.2 ± 0.72.2 ± 0.62.2 ± 0.71.9 ± 0.62.3 ± 0.81.3 ± 0.92.2 ± 0.9
Spongiosis2.6 ± 0.92.6 ± 0.73.2 ± 0.53.4 ± 0.52.7 ± 0.73.1 ± 0.52.6 ± 0.92.1 ± 0.82.7 ± 1.02.2 ± 1.21.5 ± 0.8
Neuronal loss2.6 ± 0.62.3 ± 0.71.9 ± 0.61.8 ± 0.62.4 ± 0.72.2 ± 0.62.2 ± 0.81.9 ± 0.62.2 ± 0.80.8 ± 0.81.4 ± 0.6
  • Results as mean ± SD. 0, no changes; 1, mild changes; 2, moderate changes; 3, severe changes; 4, maximal changes.

Discussion

In the present study, the sequential cases from systemic surveillance with consistent data collection in one country were analysed. Similar to the study of Parchi et al. (1999), which reported the MV2 subtype in 9% of investigated sCJD cases, we found this subtype in 12% of German sCJD patients. Since kuru plaques were found in all our MV2 patients (Parchi et al., 1996), the MV2 subtype corresponds to the 3MV subtype of the classification of Collinge et al. (1996; Hill et al., 2003). The PrPSc typing was carried out in all patients in whom frozen brain tissue was available independently from clinical features or other peculiarities of the concrete cases. However, we cannot completely exclude the possibility that some abnormal phenotypes such as cases with very long disease duration were not referred to the Surveillance Unit by external physicians because of a clinical misdiagnosis.

In line with the earlier study, dementia and ataxia were present in all patients and also the most frequent initial clinical symptoms (Parchi et al., 1999). The cortical visual disturbances previously not reported in the MV2 subtype were found in two of our patients as an initial symptom and in one patient during the later disease course (Parchi et al., 1999).

All our MV2 patients developed psychiatric symptoms during the disease course. The prevalence of psychiatric symptoms in our patients was clearly higher than that reported previously both for the MV2 subtype and typical sCJD, but very similar to that in variant CJD (vCJD) (Lundberg, 1998; Parchi et al., 1999; Will et al., 2000). In contrast to vCJD, only few MV2 patients initially presented with psychiatric symptoms (Will et al., 2000). However, in 18% of our patients a psychiatric or psychosomatic disease was the first diagnosis suspected. The high prevalence of psychiatric symptoms may be explained by the slow disease progression, which enabled the patients to report their psychiatric problems.

The frequency of extrapyramidal signs in the present study was higher than in MV2 patients and unselected sCJD reported previously (Parchi et al., 1999; Zerr and Poser, 2002). In contrast, lower prevalence of pyramidal signs was found (Parchi et al., 1999; Zerr and Poser, 2002). Similar to the findings in a larger sCJD patient group, 18% of our patients developed sensory symptoms (Meissner et al., 2004). This was much higher than in the earlier study on the MV2 subtype, but clearly lower than in vCJD (Parchi et al., 1996; Collie et al., 2001).

Myoclonus is a characteristic sign, which often leads to the suspicion of sCJD for the first time. In line with a previous study, myoclonus occurred in our patients as late as 7.5 months (median) after disease onset and was less frequent than reported for all sCJD patients (Parchi et al., 1999; Zerr and Poser, 2002).

In order to ensure a degree of consistency in clinical assessments we compared the clinical features in our MV2 patients with those in other sCJD subtypes included in the German CJD Surveillance Study (Table 8). While dementia was present in almost all patients in each subtype investigated, ataxia was significantly more frequent than in MV1, MM2 and VV1 patients. Myoclonus in our MV2 cases was significantly more rare than in MM1 cases. Pyramidal signs were less frequent than in other sCJD subtypes. Extrapyramidal signs were significantly more common than in the VV1 and VV2 subtypes. Frequency of visual symptoms in our MV2 patients was not significantly different from that in other subtypes.

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Table 8

Frequency of the main symptoms (%) during disease course in different sCJD suptypes (German CJD Surveillance Study)

sCJD subtypenAge at onset (years)*Disease duration (months)*DementiaAtaxiaMyoclonusPyramidalExtrapyramidalVisual/oculomotor
MV22664 (53–75)12 (4–27)10010069348847
MM18367 (31–86)n.s.14 (1–38)P < 0.001299n.s.390n.s.394P = 0.002378P < 0.001381n.s.363n.s.3
MV11261 (53–79)n.s.15 (2–20)P<0.0012100n.s.467P = 0.007492n.s.467n.s.492n.s.425n.s.4
MM2a1267 (60–82)n.s.114 (3–24)n.s.1100n.s.467P = 0.007492n.s.483P = 0.013492n.s.433n.s.4
VV22767 (55–81)n.s.17 (2–14)P < 0.001296n.s.4100n.s.463n.s.444n.s.452P = 0.006459n.s.4
VV1b944 (19–55)P < 0.001221 (10–49)P = 0.0072100n.s.456P = 0.002456n.s.478P = 0.05467P = 0.003422n.s.4
  • aKrasnianski et al. (2006); bMeissner et al. (2005); P, statistical significance of frequency of each clinical feature compared with that in the MV2 subtype: 1Student t-test; 2Mann–Whitney rank sum test; 3chi-square test; 4Fisher exact test; n.s., not significant; *as median and range.

Summarizing, frequency of some neurological and psychiatric abnormalities revealed in our patients was higher than that reported previously. We cannot entirely exclude that it might be due to a more detailed clinical assessment in our study. However, some symptoms and signs such as the cortical visual impairment not previously reported in the MV2 subtype were very distinct. The relatively high number of patients with the MV2 subtype in the present study may be a possible cause for these discrepancies.

In contrast to the previous studies involving smaller numbers of MV2 patients, which reported a 14-3-3 protein sensitivity of 30 and 57%, we found a higher sensitivity of 76%. This was still lower than in typical sCJD (Zerr et al., 2000b; Zerr and Poser, 2002; Castellani et al., 2004). Repetitive LPs led to detection of 14-3-3 proteins in two of the three initially negative patients. Thus, repetitive LPs can help to support the diagnosis in the MV2 subtype. The negative LP results were obtained not significantly earlier than the positive, and one of the three patients remained 14-3-3 protein negative in spite of repeated punctures. It may be presumed that the stage of disease when the LP was performed is not the only cause for lower 14-3-3 protein sensitivity in the MV2 subtype. No obvious correlation between severity of histological changes and 14-3-3 test sensitivity was found (Castellani et al., 2004). Longer disease duration and slow disease progression were proposed as possible causes, but high 14-3-3 test sensitivity was also reported in a larger group of younger non-MV2 sCJD patients with prolonged disease course (Castellani et al., 2004; Boesenberg et al., 2005).

Interestingly, the sensitivity of tau-protein was the highest among all CSF markers evaluated, but still lower than in a previous study on unselected sCJD patients (Otto et al., 1997). The simultaneous tau- and 14-3-3 protein investigation showed the highest sensitivity among all surrogate CSF markers (89%) and can be regarded as useful in the diagnosis of the MV2 subtype.

Prolonged disease duration, monosymptomatic disease course for at least 6 months in some patients, late and relatively rare occurrence of myoclonus, and absence of PSWCs may be responsible for the late sCJD diagnosis in MV2 patients. Sporadic CJD was initially proposed in none of the MV2 patients in this study and was suspected for the first time 8 months after the disease onset.

The MRI was the most useful diagnostic test in our patients. In line with a previous study, the sensitivity of MRI for basal ganglia hyperintensities in MV2 patients was very high (90% for T2- and 100% for DWI-, FLAIR- and PD-weighted scans) (Meissner et al., 2004). Only limited data on MRI changes of the thalamus in sCJD have been published so far (Collie et al., 2001). No thalamic hyperintensities could be detected in any scan of our MM1 control group. Hyperintensities of the pulvinar were detected in 7 of our 10 patients with FLAIR imaging (70%) and in 7 of 8 patients with available DWI (88%). In comparison, a previous study on different CJD subtypes, which included only one patient with a known MV genotype (prion protein type was not defined), detected thalamic hyperintensities on DWI in 12.5% of patients investigated (Shiga et al., 2004). These changes were also observed in a further study in 34% on FLAIR and DWI (Young et al., 2005). However, the sCJD subtype was not reported. Therefore, it could be speculated that these findings may be due to a high proportion of MV2 patients (Young et al., 2005). While one patient showed a classical pulvinar sign as found in 78% of vCJD patients, thalamic hyperintensities in other patients were clearly visible but not more prominent than those in basal ganglia (Collie et al., 2001). Additionally, hyperintense dorsomedial thalamic nuclei could be found in three out of four of our patients with a positive PD-weighted MRI (Fig. 1) resembling the ‘hockey stick sign’ described in vCJD patients (Zeidler et al., 2000). A classical pulvinar sign was reported in a patient with the VV1 subtype (Zeidler et al., 2000), and pulvinar hyperintensities less prominent than in basal ganglia were observed in a further VV1 and two MV2 patients (Haik et al., 2002; Martindale et al., 2003; Rossetti et al., 2003; Petzold et al., 2004). Such a high frequency of distinct thalamic hyperintensities (up to 88% on DWI in our patients) has not been reported for any sCJD subtype including previous studies on the MV2 subtype (Zerr et al., 2000b; Meissner et al., 2004).

Compared with results of diagnostic tests in other sCJD subtypes included in the German CJD Surveillance Study, the lowest 14-3-3 protein sensitivity, but the highest MRI sensitivity was obtained in the MV2 subtype. The EEG had a high diagnostic value only in the MM1/MV1 subtype (Table 9).

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Table 9

Sensitivity of diagnostic tests in different sCJD suptypes (German CJD Surveillance Study)

sCJD subtypeEEG (%)MRI (BG) (%)14-3-3 (%)
MV22/26 (8)18/20 (90)17/25 (76)
MM165/78 (83)P < 0.001236/71 (51)P = 0.002167/69 (97)P < 0.0011
MV17/11 (64)P < 0.00115/7 (71)n.s.111/12 (92)n.s.1
MM2a5/12 (42)P = 0.02212/8 (25)P = 0.002110/11 (91)n.s.1
VV21/21 (5)n.s.115/22 (68)n.s.125/27 (93)P = 0.0361
VV1b0/9 (0)n.s12/7 (29)n.s.18/8 (100)P < 0.0011
  • aKrasnianski et al. (2006); bMeissner et al. (2005); BG, basal ganglia hyperintensities; P, statistical significance of frequency of each diagnostic test compared with that in the MV2 subtype: 1Fisher exact test; 2chi-square test; n.s., not significant.

The codon 129 polymorphism was shown to influence the sensitivity of diagnostic tests in sCJD. The prevalence of PSWCs in EEG was significantly lower in MV and VV CJD patients (Zerr et al., 2000b). Heterozygotes had also a significantly lower 14-3-3 protein sensitivity (Zerr et al., 2000b; Castellani et al., 2004). In contrast, the likelihood of a positive MR scan was higher in MV patients, but also in those with VV genotype (Meissner et al., 2004). Codon 129 heterozygosity as well as the prion protein type 2 were found to be associated with longer disease duration (Pocchiari et al., 2004). No clear influence of the prion protein type on MRI sensitivity was reported so far, although slight tendency towards higher MRI sensitivity seems to exist in patients with the prion protein type 2. EEG and protein 14-3-3 sensitivity was higher in the prion protein type 1 (Zerr et al., 2000b; Castellani et al., 2004). These findings correspond to the results obtained in the MV2 patients included in this study.

About 25% of our MV2 patients could be classified either as possible sCJD or as possible vCJD and one patient as probable vCJD or probable sCJD according to WHO criteria (WHO, 1998, 2001; Will et al., 2000). This particular patient presented with progressive neuropsychiatric disorder of more than 6 months duration (8 months). He showed such early psychiatric symptoms as delusions and social withdrawal as well as ataxia, myoclonus and dementia required by WHO criteria for vCJD. The patient also had no PSWCs in EEG, and bilateral pulvinar sign on MRI was detected. Although the patient fulfilled WHO criteria for probable vCJD, he developed ataxia and dementia as early as 2 months after symptom onset, did not show any sensory symptoms and was 62 years old. The 14-3-3 test was positive. These facts suggested the diagnosis of probable sCJD, rather than of probable vCJD, but did not contradict vCJD criteria.

Histological changes were predominantly found in the thalamus, basal ganglia and limbic cortex. In addition to a significant correlation between disease duration and cortical involvement also reported in the previous study (Parchi et al., 1999), a significant correlation between disease duration and nerve cell loss was found in the pulvinar in our MV2 patients. A high degree of gliosis in the pulvinar supports the hypothesis of gliosis as the pathological correlate of the high thalamic signal intensity (Collie et al., 2003). According to a previous study, the MM1 subtype not associated with the pulvinar sign shows a lower thalamic gliosis rate (Parchi et al., 1999). Although the vermis in MV2 patients in the present and previous studies showed relatively mild pathological changes, severe gait and trunk ataxia was one of the most prominent clinical features (Parchi et al., 1999; Zerr et al., 2000b). Pronounced pathology of the frontal cortex suggested an impairment of the frontopontocerebellar tract as one of the possible explanations for the severe ataxia in the MV2 subtype (Terry and Rosenberg, 1995). Consistent with previous studies, kuru plaques were found in all patients (Parchi et al., 1999; Zerr et al., 2000b). These changes are also found in kuru, a prion disease transmitted by cannibalism in New Guinea, and are reminiscent of the ‘florid plaques’ typically detected in vCJD (Gajdusek and Zigas, 1957; Will et al., 1996). However, the reasons for such changes in the MV2 subtype of sCJD are unknown.

Conclusion

At least one of the three diagnostic tests, i.e. MRI, tau and 14-3-3 protein studies, was positive in all patients investigated and supported the clinical sCJD diagnosis. The MRI was very sensitive in MV2 patients, and thalamic hyperintensities were observed significantly more frequently than in typical sCJD. Prolonged disease duration, early and prominent psychiatric symptoms, lack of PSWCs, thalamic hyperintensities on MRI and rather low 14-3-3 protein sensitivity in the MV2 subtype delay the sCJD diagnosis and may be suspicious for vCJD. Many features of the MV2 subtype seem to be more similar to those of vCJD than sCJD. However, distinct sensory symptoms and young age at onset are not common in the MV2 subtype, and the classical pulvinar sign frequently found in vCJD was detected in only one of our MV2 patients.

Acknowledgments

The authors thank Ms Bodemer, Ms Ciesielczyk, Ms Henn and Ms Staniszewski for technical assistance. The assistance of Ms Zellner and Ms Schneider-Dominco is gratefully acknowledged. The authors thank Dr R. G. Will (Edinburgh) for his helpful comments on the manuscript. This study was supported by grants from the Federal Ministry of Health and Social Security (325-4471-02/15), the European Commission (QLG3-CT-2002-81606), and the Federal Ministry of Education and Research (01GI0301).

References

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