An article takes you through the "Tiger's Eye Sign".
Tiger eye sign refers to the bilateral paleoglobule with a significant low signal on the axial T2WI sequence of the brain MRI examination, and a strip of flaky high signal can be seen in the anterolateral low signal of the paleosphere, which is very similar to the tiger's eye overall, called tiger eye sign.
Of course, some people say that they don't feel like the eyes of a tiger, so someone gave such an explanation. Flip the image 180° and look again, perhaps more like a tiger's eyes.
The low T2 signal of the pale bulbs in tiger's eye sign is mainly associated with iron deposition. With the increase of age, normal people will have iron deposition, of which the nucleus such as globus pallets, red nuclei, and substantia nigra is the most obvious. This deposited iron is mainly in the form of ferritin, which is a paramagnetic substance, so it behaves as a low signal on the T2WI sequence.
Some vertebral extraphyllal diseases such as globus globus pigment degeneration syndrome, Parkinson's syndrome, etc. will accelerate the rate of iron deposition in the nervous system, and in young people, it will be manifested as a bilateral globus globus with obvious T2WI low signal; and it will also cause intraterrestrial glial hyperplasia, increased water content, neuronal disintegration and disappearance, and neural fiber reticulosal formation, showing a significantly high signal on the T2WI sequence.
The most common extravertebral disorder with this tiger's eye sign is pantothenic kinase-associated neurodegeneration (PKAN), which was previously known as bulbous paleochromatosis syndrome and is a rare childhood familial recessive inherited neurodegenerative disorder. Tiger eye sign is a specific manifestation of Hallevorden-Spatz disease (HSD).
Pathologically, globus pal, abnormal deposition of iron in the substantia nigra, loss of neurons, and axon degeneration may be seen. The anterior interior of the bulbous globus pllidus and the head of the caudal nucleus showed loose tissue changes, which were markedly vacuo-like degeneration, but lacked iron deposition.
HSD occurs more often than in children or adolescents, progresses rapidly, and is mainly manifested as vertebral and extravertebral symptoms, mental consciousness disorders, and language disorders. The low T2WI signal of the globus pallets in MRI corresponds to the pathological pigmentation and the swollen area of the neuronal axon, due to the paramagnetism of the iron, while the high signal represents the pathologically loose tissue region. In addition to the globus pallidus, lesions can also involve red nuclei, dentate nuclei, and also present with low T2WI signal.
Young patients, two-handed postural tremor for more than 10 years, physical examination found that the patient is a mask face, the voice is monotonous.
Brain MRI is performed. Axial T2-FLAIR sequence showing flaky hyperinflation in a bilateral globus pallet low-signal background, the patient is eventually diagnosed with atypical PKAN.
Female, 21 years old, repeated falls, progressive exacerbation of spasms.
Difficulty in constituting sounds for the past three years, and there is a history of epilepsy after fever 10 years ago. Patients describe their brothers with similar symptoms and radiographic findings. MRI examination of the T2WI sequence shows bilateral symmetry of the glomeruli high signal surrounded by a low signal, called a tiger eye sign. The patient was eventually diagnosed with PKAN.
In short, tiger's eye sign refers to the high signal caused by the diffuse T2WI low signal caused by bilateral pale ductile iron deposition due to neuron disintegration and disappearance, keratin hyperplasia, nerve fiber reticulocalis, etc., resembling tiger's eye. The presence of tiger's eye sign is highly suggestive of pantothenic acid kinase-associated neurodegenerative disorders (PKAN).
Iron deposition neurodegenerative diseases of brain tissue (NBIA)
Overview: Refers to a group of genetic diseases of the nervous system caused by specific gene mutations, the clinical manifestations are mainly movement disorders, gait abnormalities, spasms, cognitive impairment, etc., and their common imaging features are abnormal iron ion deposition signals in specific parts of the brain.
NBIA is diagnostic imaging, and its multiple types of diseases can cause:
1, PKAN: that is, the above HSD: accounting for about 50%.
2. PLAN: PLA2G6-related neurodegenerative diseases, accounting for 20%.
3. MPAN: Mitochondrial membrane protein-related neurodegenerative disease.
4. Kufor-Rakeb disease (KRD).
5. FAHN/SPG35: FA2H-associated neurodegenerative disease.
6. BPAN: helipsin-related neurodegenerative disease.
7. Woodhouse-Sakai syndrome (WSS).
8. Ceruloplasmin deficiency (ACP).
9. Neuroferrinosis.
10. Adolescent static encephalopathy Adult neurodegenerative disease: SENDA.
11. Neuroaxical dystrophy: NAD.
Previous classifications of NBIA are based on family history, age of onset, and histopathological manifestations. At present, with the in-depth study of this group of diseases and the discovery of related pathogenic genes, attempts have been made to confirm specific types according to genotype. Attach a diagnostic flowchart and some differentiating points.
The above is the classification and identification of specific types of NBIA, in addition, NBIA needs to be distinguished from other diseases that present as extrapyramidal:
1. If the disease occurs in childhood: it is distinguished from cerebral palsy, carbon monoxide or mold sugarcane poisoning, and extrapyramidal symptoms caused by drugs.
2. If the course of progressive disease is progressive, It is necessary to exclude Wilson's disease, Huntington's disease, deformed dystonia and juvenile waxy lipid brownosis (ceroid lipofuscinosis), and physiological calcification and Fahr syndrome should also be excluded.
3. Patients with elderly disease should pay attention to distinguishing them from Parkinson's disease.
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