Indian Journal of Radiology and Imaging Indian Journal of Radiology and Imaging

NEURORADIOLOGY & HEAD AND NECK IMAGING
Year
: 2018  |  Volume : 28  |  Issue : 2  |  Page : 152--160

Imaging of dentate nucleus pathologies; a pictorial essay


Kajari Bhattacharya, Hima Pendharkar, Arun K Gupta 
 Department of Neuroimaging and Interventional Radiology, NIMHANS, Bengaluru, Karnataka, India

Correspondence Address:
Dr. Hima Pendharkar
Department of Neuroimaging and Interventional Radiology, NIMHANS, Hosur Road, Bengaluru, Karnataka - 560 029
India

Abstract

Dentate nucleus is affected in a wide variety of conditions. Magnetic resonance imaging of the brain is the diagnostic modality of choice for delineating the signal characteristics, which helps in narrowing down a vast list of differentials for conditions affecting the dentate. Computed tomography plays an important role, especially for pathologies associated with calcification of dentate nucleus.



How to cite this article:
Bhattacharya K, Pendharkar H, Gupta AK. Imaging of dentate nucleus pathologies; a pictorial essay.Indian J Radiol Imaging 2018;28:152-160


How to cite this URL:
Bhattacharya K, Pendharkar H, Gupta AK. Imaging of dentate nucleus pathologies; a pictorial essay. Indian J Radiol Imaging [serial online] 2018 [cited 2020 Apr 5 ];28:152-160
Available from: http://www.ijri.org/text.asp?2018/28/2/152/235420


Full Text



 Introduction



Dentate nucleus is the largest of deep cerebellar nuclei. It has a predictable imaging appearance with respect to the surrounding cerebellar white matter during the first year of life. At term it is hypointense on T1 and hyperintense with a dark serrated rim on T2. By 6 months of age, it remains slightly brighter on T2-weighted (T2W) images and the hypointense rim cannot be separately distinguished from the surrounding cerebellar white matter.[1] Therefore, increased signal in dentate nucleus on T2W or fluid-attenuated inversion recovery (FLAIR) sequences beyond 6 months is abnormal. Diffusion restriction at any age is abnormal.[2]

Numerous conditions can affect the dentate nuclei. A recent review [3] elucidated the clinico-radiological approach to aid the diagnosis and management of these conditions. Careful assessment of the differential involvement of dentate hilus, peridentate white matter, rest of the cerebellar white matter, cerebellar gray matter and brainstem, and supratentorial abnormalities can help narrow down the possibilities.

We present a pictorial review of the various pathologies affecting dentate nuclei and their imaging findings encountered in our institute.

Role of computed tomography

The role of computed tomography (CT) is well established in identifying the variety of conditions known to cause calcifications in the dentate nuclei [Table 1].[4] If present, it narrows down the differential diagnosis in accordance with the age at presentation, history, and clinical features.{Table 1}

Role of magnetic resonance imaging

For eliciting the subtle signal changes in the dentate with associated abnormalities of the rest of the brain and spinal cord, magnetic resonance imaging (MRI) is the investigation of choice. Sequences which are routinely acquired include T1, T2, susceptibility-weighted imaging (SWI)/gradient echo (GRE), diffusion-weighted imaging (DWI) and postcontrast T1W imaging.

Conditions affecting dentate nuclei and their imaging appearance

These conditions have been elaborately described by Van der Knaap [5].

Leukodystrophies

Krabbe's disease or globoid cell leukodystrophy is an autosomal recessive disorder caused by the deficiency of galactocerebroside β-galactosidase causing accumulation of cerebroside in lysosomes of white matter forming characteristic globoid cells. Subtypes include early infantile (most common), late infantile onset, juvenile, and adolescent. CT plays an important role as bilateral hyperdense thalami are a characteristic feature of this entity. MRI shows T2/FLAIR hyperintensity in the periventricular white matter and occasionally optic nerve/chiasma hypertrophy. Dentate may be involved. Postcontrast images may show nerve enhancement [Figure 1].{Figure 1}

Alexander's disease is a nonfamilial leukoencephalopathy presenting in, infantile, juvenile, or adult forms. Most reported cases are infantile onset presenting with global developmental delay. Characteristic MRI findings include extensive supratentorial white matter hyperintensities with frontal predominance and involvement of subcortical white matter. Signal changes are also noted in the basal ganglia. T1 hyperintense, T2 hypointense capping is noted adjacent to the frontal horns bilaterally. Postcontrast images reveal enhancement of the periventricular rim and the dentate nucleus [Figure 2].{Figure 2}

Canavan's disease or spongiform leukodystrophy is an autosomal recessive disorder caused by the deficiency of N-acetylaspartylase (NAA). The condition is characterized by early onset macrocephaly. MRI shows diffuse T2/FLAIR hyperintensity in the supratentorial white matter. Globus pallidus is involved. Magnetic resonance spectroscopy (MRS) shows a large NAA peak [Figure 3].{Figure 3}

Aicardi–Goutiere's syndrome is an autosomal recessive disorder characterized by microcephaly, chronic cerebrospinal fluid (CSF) lymphocytosis, and raised levels of CSF interferon-α. Onset is typically in the first year of life with feeding difficulties, low-grade fever, progressive truncal hypotonia, severe pyramidal and extrapyramidal signs, and skin lesions. MRI may show diffuse white matter hyperintensity in T2/FLAIR with punctate calcifications. Cystic change is known in this entity [Figure 4].{Figure 4}

Metabolic, toxin, and drug-induced

Maple syrup urine disease shows enzymatic defect in the initial steps of the common metabolic pathway for breakdown of branched-chain amino acids – leucine, isoleucine, and valine – leading to the accumulation of corresponding keto acids. Infants generally present with failure to thrive. CT shows a very characteristic pattern with profound hypodensity and swelling of the cerebellar hemispheres including dentate, dorsal part of the pons, midbrain, posterior limb of the internal capsule, the globus pallidus, and often the thalamus. These areas appear hyperintense in T2 and show diffusion restriction. MRS shows elevated branched chain amino acids and ketoacids at 0.9 ppm [Figure 5].{Figure 5}

Cerebro-tendinous xanthomatosis is a rare autosomal recessive disorder of lipid metabolism, characterized by tendon xanthomas, early cataracts, mental deterioration, and spastic-ataxia. Involvement of spinal cord is also noted in some cases. CT may show dentate calcifications. MRI shows characteristic trilaminar appearance of the dentate, as shown in [Figure 6]. Hyperintense signal is also noted in supratentorial white matter, especially along the posterior limbs of internal capsules.{Figure 6}

L-2 hydroxyglutaric aciduria has an autosomal recessive mode of inheritance. The age of presentation is relatively older than that of Canavan's disease. It is characterized by elevated levels of l-2-hydroxyglutarate in urine, CSF, and plasma. Imaging shows T2/FLAIR hyperintensity of the subcortical white matter, sparing the deep white matter. Globus pallidus, caudate, and putamen are typically involved. Dentate may be involved. Diffuse gliomas have also been reported with the condition [Figure 7].[6]{Figure 7}

Glutaric aciduria type 1 is an autosomal recessive metabolic disorder caused due to the deficiency of glutaryl CoA dehydrogenase enzyme. Most cases present during infancy with acute encephalopathic illness along with seizures, hypotonia, and choreoathetosis precipitated by fever, immunization, or surgical procedure. MRI shows a large head size with wide open sylvian fissure due to failure of operculization, signal changes in the basal ganglia, and bilateral subdural collections. Dentate may be occasionally involved [Figure 8].{Figure 8}

Mucopolysaccharidoses represent a group of inherited lysosomal storage disorders characterized by defective degradation of glycosaminoglycans. The clinical manifestations include short stature, skeletal deformities, hepatosplenomegaly, hernias, coarse facial features with cardiovascular, respiratory, and neurological abnormalities. MRI may show large head size, with J-shaped sella, prominent perivascular spaces, and crowding at Foramen magnum. Dentate may be involved [Figure 9].{Figure 9}

Metronidazole toxicity is a known cause of abnormal T2 hyperintense signal change in dentate nuclei. This toxicity generally presents with dysarthria, ataxia, and visual blurring. Cumulative dose of 25–90 g administered over a period of 1–3 months is implicated.[3] Symptomatic as well as imaging reversal is noted post drug withdrawal [Figure 10].{Figure 10}

Isoniazid-associated cerebellitis has been described in patients on antitubercular treatment with coexistent chronic renal disease. It can present with bilateral dentate T2/FLAIR hyperintensity and diffusion restriction. Follow-up after withdrawal generally shows resolution of signal changes.[7]

Fahr's syndrome is an autosomal dominant disorder, presents in 4th to 5th decade characterized by progressive neurologic dysfunction and neuropsychiatric manifestations. Biochemical abnormalities and somatic features suggestive of a metabolic disease or infectious, toxic, and traumatic causes should be excluded. Extensive calcifications can be seen in the subcortical white matter, basal ganglia, and dentate, as shown in [Figure 11].{Figure 11}

Chronic lead poisoning is seen most commonly due to occupational exposure in workers involved in the manufacture of lead pipes and batteries. They can present with nonspecific neurologic manifestations such as dementia, diminished visual acuity, peripheral neuropathy, syncope, dizziness, nystagmus, easy fatigue, and back pain. It can be associated with extensive intracranial calcifications [Figure 12].[8]{Figure 12}

Leigh disease or subacute necrotizing encephalomyelopathy is a progressive neurodegenerative disorder caused by mitochondrial respiratory enzyme chain defects, characterized by developmental regression, and is often associated with febrile episodes and is caused by enzyme deficiencies of the respiratory chain complexes [Figure 13]. T2 hyperintensity is noted in the basal ganglia, brainstem, and dentate nuclei with diffusion restriction and postcontrast enhancement, which may be seen in acute stages. Involvement of brainstem and subthalamic nuclei has been described as an indicator of SURF-1 mutations in cases of cytochrome oxidase deficiency.[9]{Figure 13}

Wilson's disease is an autosomal recessive disorder with defect in copper metabolism; it is characterized by abnormal accumulation of copper in various tissues, particularly in the liver and brain. Flapping tremors are classical findings in neurological examination along with Kaiser–Fleischer ring. MRI shows signal changes in basal ganglia, brainstem, and dentate, with occasional hyperintensity of cortex and subcortical white matter, especially frontal lobes [Figure 14].{Figure 14}

Neurodegenerative

Neurodegeneration with brain iron accumulation (NBIA) is a group of progressive neurological disorders that present with prominent extrapyramidal symptoms, intellectual impairment, and iron deposition in basal ganglia. Ten forms of NBIA have been described to date,[10] of which neuroferritinopathy and aceruloplasminemia have been associated with iron deposition in dentate nuclei [Figure 15] and [Figure 16].[11]{Figure 15}{Figure 16}

Inflammatory and infectious

Progressive multifocal leukoencephalopathy is a fulminating opportunistic infection of the brain caused by John Cunningham virus (JC virus) in a setting of immunocompromised status leading to myelin breakdown and oligodendrocyte destruction.[5] Diffuse but bilateral asymmetrical signal changes are noted in the supra- and infratentorial white matter with involvement of subcortical areas [Figure 17]. Occasional postcontrast enhancement may be seen.{Figure 17}

Langerhans's cell histiocytosis (LCH) presents with reactive clonal proliferation of Langerhans cells, which are bone marrow-derived cells of dendritic cell line with antigen presenting and processing properties. CNS imaging reveals craniofacial bones, skull base and paranasal sinus invasion, involvement of meninges and hypothalamo-pituitary axis is noted.[12] Patchy lesions with postcontrast enhancement may be seen; involvement of dentate is common [Figure 18].{Figure 18}

Erdheim–Chester disease is a non-Langerhans cell form of histiocytosis characterized by xanthomatous infiltration of tissues by foamy histiocytes. Multiple organ infiltration is also noted in this entity, as in LCH. Diametaphyseal osteosclerotic lesion of long bones showing increased uptake in Tc 99m bone scintigraphy form radiological diagnostic criteria. Dentate involvement has been described in this entity.[13]

Multiple sclerosis (MS) is the most common chronic inflammatory demyelinating disease affecting young adults mostly leading to severe and irreversible clinical disability. The demyelinating plaques can be noted in the supratentorial (periventricular and juxtacortical) as well as infratentorial parenchyma and spinal cord. Dentate involvement has been described as T1 hyperintensity in unenhanced images, which are more commonly associated with the secondarily progressive subtype.[14] T2 hypointensity in dentate has also been correlated with ambulatory impairment in MS.[15] [Figure 19].{Figure 19}

Miscellaneous

Gadolinium-based contrast agent (GBCA) exposure – Of the other causes of dentate involvement, gadolinium deposition in dentate nuclei is important. It can be observed in patients who require repeated imaging with GBCAs. The patients generally have preserved renal function. Deposition is also seen in the globus pallidus and is most commonly associated with use of gadodiamide (nonionic linear chelate). It is now considered that the T1 hyperintensity in the dentate nuclei of MS patients may be attributed to the repeated exposure to GBCAs and gadolinium deposition given the repeated MRI done in these patients.[16] Recent studies performed on autopsy specimens proved that T1 shortening results from gadolinium retention in neuronal tissues of the global pallidus, thalamus, dentate nucleus, and pons [Figure 20].{Figure 20}

 Conclusion



We have presented the dentate involvement in many commonly encountered conditions in neuroradiology practice. Awareness of the conditions and imaging with CT and MRI individually or in conjunction with each other leads to the most plausible diagnosis in almost all instances.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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