1. XIX Symposium Neuroradiologicum 4-9 October, 2010 Bologna Italy
MRI findings in patients with clinical onset consistent with Infantile Neuroaxonal Dystrophy (INAD), literature review, clinical and MRI follow-up
1 Paediatric Neuroradiology, Dept. of Neurosciences, Bologna
2 Child Neurology and Psychiatry, Maggiore Hospital, Bologna
3 Child Neurology and Psychiatry, University of Bologna
4 Clinical Dept. of Rad. and Histopathol. Sciences, University of Bologna
5 Movement Disorders & Energetic Metabolism Diseases, Neurological Institute Besta, Milano
6 Child Neurology and Psychiatry, S. Orsola Hospital, Bologna
7 Paediatric Neurology, Policlinico Hospital, Modena
8 Paediatric Neurology, S.Anna Hospital, Ferrara
B.Bernardi1, A.Pini2, M.Santucci3, C.Cenacchi4, B.Garavaglia5, V.Ucchino1,
C.Garrone6, A.Guerra7, R.Faggioli8, C.Barzaghi5, P.Preda4, E.Franzoni6,
G.Gobbi2, A.Parmeggiani.3

2. Infantile neuroaxonal dystrophy (INAD)
Rare neurodegenerative disorder involving axons in both central and peripheral nervous systems.
Infantile onset between 6 mos. and 2 yrs. Arrest and rapid regression of motor and cognitive developmental milestones, hypotonia evolving into spastic tetraplegia, cerebellar ataxia and early visual impairment with abnormal visual evoked potentials.
Chronic denervation confirmed by EMG.
Epilepsy has been reported in few cases, EEG can show high-voltage fast rhythms.
Pathological hallmarks: axonal swelling and spheroid bodies (SB) in the pre-synaptic terminals. Nevertheless, SB can be found in other degenerative disorders and are not detected in all tissue specimens of INAD patients.

3. Infantile neuroaxonal dystrophy (INAD)
80% of INAD had mutations in the PLA2G6 gene (22q12.3-q13.2) encoding a calcium-independent phospholipase A2 enzyme.
More recently, it has come to light that mutations in the same gene are responsible for some cases of idiopathic neurodegeneration with brain iron accumulation (NBIA).
Evidence that a large percentage of INAD patients have a mutation in the PLA2G6 gene, allows molecular diagnosis and often negates the need for biopsy, an invasive procedure.
On the other hand, the genetic analysis of some patients with typical clinical and pathological features of INAD are negative for PLA2G6 mutations, suggesting the possibility of a genetic heterogeneity for these INAD phenotypes.

4. PURPOSE
We retrospectively reviewed the MR studies at the onset and during the follow-up of 8 patients in whom clinical and imaging onset met the typical criteria for INAD. The authors compared these data with those reported previously in literature.
Aim of the study was to define if MR features are useful and sufficient in differentiating INAD from other diseases with a similar clinical presentation, guiding clinicians towards appropiate molecular diagnostic testing and to discuss which are the earliest and most important features suggesting INAD diagnosis.

5. Table 1 Clinical features, biopsy and PLA2G6 mutation screening results

6. INAD: MR findings MR signs investigated were:
extension & topography of cerebellar atrophy (inclusive criterion)
cerebellar T2 hyperintensity
optic pathway atrophy.
T2 signal of the GP and substantia nigra/subthalamic nuclei
cerebral white matter abnormalities & cerebral atrophy
corpus callosum changes
The MR follow-up of 7 patients included: H+MRS, diffusion MR Imaging (DWI), and diffusion tensor (DTI) analysis.

7. Cerebellar progressive atrophy and T2 hyperintensity
Diffuse and progressive cerebellar atrophy in all 8 patients.
High T2 signal of the cerebellar cortex in six of eight patients.
Patient 1 with a heterozygous variant of the PLA2G6 gene and + biopsy had a mild cerebellar hyperintensity not progressive and not described in the first of the 3 MRI.
Patient 4 with post mortem pathological INAD diagnosis showed a clearly detectable high T2 of the cerebellar cortex as early as the 1° MRI at 21 months of age and even higher in the follow up.

8. Single voxel left hemisphere cerebellar cortex
Patient 1
Female, age of onset 12 months. Biopsy: SB +
DNA: heterozygous indeterminate variant of PLA2G6 gene.
3rd MR, 24 months old
FLAIR T2WI A
FSE T2WI Cr mI
Cho
NAA
MRS
Single voxel left hemisphere cerebellar cortex
FSE T2WI
ADC
Patient 1
Cerebellar atrophy, high T2 signal of the cerebellar cortex
A FLAIR T2WI
B FSE T2WI
C FSE T2WI Cr mI
MRS
Single voxel
Left cerebellar
hemisphere
Cho
NAA

9. Patient 4
T1W
T1W
T1W A C E B D F
T2W
T2W
T2W
1° MRI (A,B ) at 21 months of age,
2° MRI (C,D) at 28 months of age,
3° MRI (E,F,G) at 5 years and 7 months of age.
Progressive cerebellar and corpus callosum atrophy, cerebellar cortex hyperintensity. G
PDW
T1WI

10. Cerebellar T2 hyperintensity
High T2 of the cerebellar cortex was also present in patients 2,5,6 and 8 without genetic or biopsy results supporting INAD diagnosis. The first had negative PLA2G6-mutation and clinical and MRI follow-up that became inconsistent with INAD diagnosis. The others were negative for PLA2G6 and PANK2 mutations.
Patient 3 without genetic evaluation for INAD and with negative biopsy as well as patient 7 with negative genetic investigation and biopsy, did not show any significant cerebellar hyperintensity.
T2 cerebellar cortex hyperitensity, initially considered as pathognomonic of the disease, it is not always present, and it may appear only in a later phase, likely resulting from gliosis.
In our group of patients:
Clinical onset from 4 to 15 months of age
Median age of first MRI 17.8 months (range 10 to 23 months)

11. Cerebellar atrophy high T2 signal of the cerebellar cortex
Patient ° MRI: 17 months Male, age of clinical onset 12 months: arrest acquisition milestones, ataxia, hypotonia, pyramidalism, cataracts Negative PLA2G6 and PANK2; biopsy negative
FLAIR T2WI
FLAIR T2WI
FSE-IR
Cerebellar atrophy high T2 signal of the cerebellar cortex

12. Patient 8 2° MRI 4 years and 5 months

13. Cr
Patient 8 mI
Cho
NAA
MRS LC MODE
Exp.
DWI

14. INAD but likely a common finding in different degenerative disorders.
Marinesco–Sjögren : hyperintensity of the cerebellar cortex, widened cerebellar fissures, and an enlarged fourth ventricle in the absence of basal ganglia changes
Harting, I. et al. Neurology 2004;63:
Cerebellar T2 hyperintensity, even if it is rare, is not a specific feature of
INAD but likely a common finding in different degenerative disorders.

15. Female, age of onset 12 months
Patient 3
Female, age of onset 12 months
Biopsy: negative for SB DNA: PLA2G6 not investigated 2° MRI at 3 yrs and 3 months: cerebellar atrophy, mild T2 hyperintensity of the cerebellar cortex, optic atrophy.
Patient 3. Cerebellar atrophy, mild T2 hyperintensity of cerebellar cortex, optic atrophy

16. Skin biopsy negative DNA not investigated
Patient 6 5 year-old
Skin biopsy negative DNA not investigated
Low GP signal GP GP
3 Tesla MR Unit FSE T2WI
5 year-old
age-matched
normal controls

17. Table 2 MR findings
+ Changes present (+ to ++++ indicating grading); - Changes absent; B: Changes borderline. CH: cerebellar hemisphere;
V: vermis; PV: periventricular WM; BG: basal ganglia and internal capsule; Corpus callosum: A: all CC; G genu; B: body; S: splenium corpus callosum; GP: globus pallidus; SN: substantia nigra; STN: subthalamic nuclei.

18. INAD MR relevance of MR diagnostic criteria
Since absence of either PLA2G6 mutations or pathological evidence may not exclude INAD strongly suggested by clinical features, the evaluation of MR diagnostic criteria has an increased relevance.
In clinical context consistent with the disease, progressive cerebellar atrophy, particularly but not exclusively if associated with early onset of cerebellar cortex high T2, strongly suggests diagnosis of INAD.
Optic atrophy, was evident in patients 1 and 4, both with a definitive diagnosis of INAD but it was also noted in patient 2 and less evident in patients 3 and 7. Although detectable in many other diseases, its presence increases the need to rule out INAD.
GP T2 hypointensity noted only in patient 6, is reported in NBIA patients with PANK2 mutation or in rare atypical NBIA mutations in the PLA2G6 gene. The literature does not consider this sign a crucial feature for early diagnosis of INAD.

19. INAD MR relevance of MR diagnostic criteria
High ADC in the cerebellar cortex/subcortical WM of all the 7 patients with DWI indicates neuronal loss with increased mobility of water molecules.
All the 7 patients with single voxel 1H-MRS localized in the cerebellum, showed a decreased NAA/creatine ratio.
Patient 1, the only having both, a genetically and pathologically confirmed diagnosis of INAD and Spectroscopy, had an associated high mI/Cr ratio in the same cerebellar voxel.
High mI/Cr ratio and absence of lactate also resulted in the cerebellar cortex of 5 the other 6 patients (2,5,6,7,8) without genetic or pathologic evidence of INAD, excluding patient 3 who had a slight lactate peak and a normal mI/Cr ratio.

20. CONCLUSIONS
Our study confirms that MRI should be considered a standard component of the diagnostic evaluation for INAD and other neurodegenerative disorders.
Cerebellar progressive and diffuse atrophy appears as the most characteristic MR finding in INAD and it was an inclusive criterion in our study.
The limited number of our genetically or pathologically positive patients, does not allow us to confirm that cerebellar cortex T2 hyperintensity is not an obligatory finding of the disease, because it is not always present.
The detection of this sign in patients with negative genetic or pathologic investigations for INAD, confirms that it could be a common MRI feature of many different degenerative conditions.

21. CONCLUSIONS
The increased diffusion suggests a neuronal loss as well as the low NAA/Cr common finding in the cerebellar H+MRS of all our cases.
Increased mI/Cr suggests astrogliosis a common pathologic feature detectable in late stages of different diseases.
These newer neuroimaging technologies appear to be useful in detecting abnormalities suggesting the nature of the pathological changes characterizing the disorder, but their utility has not yet been established.
At present, it is difficult on the basis of our data to find a definite correlation among clinical and neuroradiological findings with the genetic mutations; at onset and during follow-up it is necessary to study the same variables in a larger samples of patients with INAD and other neurodegenerative diseases.

22. Thank you for your attention !!