|ECR 2016 / C-1650|
|Parkinson disease and Parkinsonian syndromes: What the radiologist should know?|
|This poster is published under an open license. Please read the disclaimer for further details.|
Findings and procedure details
Idiopathic Parkison disease (PD):
Parkinson disease is a progressive neurodegenerative disease caused by primary disorder of pars compacta of substantia nigra. Clinically is characterised by bradykinesia, rigidity, tremor and postural imbalance.
PD is the main cause of the parkinsonian syndrome (80%). Most cases (85-90%) are sporadic and affect typically between 50-60 years. Nevertheless, some familiar cases have been described.
MR imaging findings are normal in early - stage of PD. In advanced stage MRI shows narrowing and loss of the normal swallow tail appearance of substantia nigra. Substantia nigra pars compacta (SNpc) loses normal hyperintensitiy and their margins become blurred (Fig.3-4).
References: Osborn. Diagnostic Imaging - Brain. Statdx.
PET and SPECT are helpful tools for distinguish PD from APS. The preservation of metabolic activity in the basal ganglio is a defining feature of PD in FDG-PET. 123 - I SPECT exposes reduced uptake in the striata. This affectation is asymmetric and more notable in posterior putamen and caudate nucleus (Fig.5).
Atypical parkinsonian syndromes:
- Multiple system atrophy (AMS)
AMS is a sporadic neurodegenerative disease characterised by neuronal loss and gliosis of nigrostriatal and olivopontocerebelar tracts. This entity combines cerebellar ataxia, autonomic dysfunction and parkinsonism. There are three clinical subtypes based on predominating symptoms: Parkinsonian type MSA (MSA-P or knows as striatonigral degeneration) and cerebellar ataxia type (MSA-C) also termed sporadic olivopontocerebellar atrophy. Shy-Drager syndrome is referred when autonomic dysfunction predominate. This entity usually develops in the 50s or 60s and symptoms do not respond to dopaminergic therapy.
There is a notable cerebellar atrophy and severe atrophy of the pons. Patients with MSA-P show putaminal atrophy, symmetric hypointensity of the dorsolateral putamen due to iron deposition and linear hyperintensity surrounding the lateral aspect of the putamen (putamen rim sign) on T2 and T2*-weighted sequences (Fig.6).
References: - Bilbao/ES
In patients with MSA-C MRI reveals selective atrophy of lower portion of basis pontis, medulla, middle cerebellar peduncle (MCPs) and cerebellar hemispheres with widening of the fourth ventricle (Fig. 7). High signal in T2 sequences in pontocerebellar tracts produce a cruciform hyperintensity in the pons knows as the hot cross bun sign (Fig.8-9). This sign has relatively high sensitivity for this entity, although it is not pathognomonic. AMS respects superior peduncle and corticospinal tracts.
References: - Bilbao/ES
With regard to nuclear imaging, FDG-PET exhibit hypometabolism in putamen in MSA-P and in cerebellar hemispheres and MCPs in MSA-C.
- Progressive supranuclear palsy (PSP)
PSP is another degenerative disease characterized by abnormal eye movements (supranuclear vertical gaze palsy) mild dementia and postural instability . The onset of PSP is insidious and with a peak age at 60 years. Other common symptoms are dysarthria, dysphagia, symmetric akinetic-rigid syndrome, neck dystonia and lurching gait.
MRI characteristic feature is atrophy of the midbrain and tegmentum.
- In sagittal T1 sequences this findings result in a flattening or concave outline to the superior aspect of the midbrain with the typical "humming bird or penguin sign". Normally the upper border of the midbrain is convex (Fig.10)
- Axial T1 sequence shows reduced midbrain anterosuperior diameter at the level of the superior colliculi and loss of the lateral convex margin on the tegmentum. This features is known as the Mickey Mouse sign (Fig.11)
References: - Bilbao/ES
Additional features include atrophic superior cerebellar peduncles, prominent mesencephalic cisterns and enlarged 3rd ventricle (Fig.12 ). In T2 images diffuse high signal in pontine tegmentum and periaqueductal is seen. Midbrain area is decreased by 50% with midbrain to pons area significantly reduced to 0.124 (normal value 0.237). MR Parkinsonism index is useful for distinguishing patients with PSP from patients with PD or MSA-P. When the value is higher than 13.55, it is suggestive of PSP (Fig.13-14).
- Corticobasal degeneration (CBD)
Corticobasal degeneration is an uncommon progressive neurodegenerative disease and it is pathologically characterized by cortical and striatal tau protein accumulation. Symptoms begin in people from 50 - 70 years. Patients present with cognitive dysfunction, myoclonic jerks and asymmetric akinetic - rigid syndrome. Also Alien limb phenomenon is an usual manifestation, as well as lack of response to levodopa.
MRI shows severe asymmetric cortical atrophy centred in posterior frontal and parietal lobes (perirolandic) with associated hyperintensity of the subcortical white matter on T2 images. FDG-PET and SPECT studies reveal hypometabolism in basal ganglia and frontoparietal lobes (Fig.15).
- Dementia with Lewy body (DLB)
DLB is a progressive presenile - onset degenerative dementia. It is the second most common neurodegenerative cause of dementia after
Alzheimer´s disease. In addition to dementia other characteristic symptoms are fluctuating cognition, visuospatial impairment with hallucinations and parkinsonism. Lewy bodies in substantia nigra, neocortex or limbic system are the pathological characteristic of the disease.
DLB radiological findings are nonspecific, like mild generalized atrophy. Medial temporal lobe is usually preserved. The main role of MRI is rule out other causes of dementia. Amyloid PET demonstrates cortical deposition and 123-I SPECT shows hypoperfusion in occipital lobe, specially in visual cortex (Fig. 16-17).
Thematically related posters
ECR 2016 / C-1355
Lymphomatosis Cerebri: MRI findings of a rare form of primary central nervous system lymphoma.
ECR 2016 / C-1019
Imaging in Neurological manifestations of Dengue virus infection- A Pictorial Review!!