1. Diffusion Tensor Imaging of Optic Nerve in Patients of Vitamin B12 Deficiency Before and After Treatment Neetu Soni, Sunil Kumar, Deepanshu Dubey, Jayantee Kalita, Sanjeev Bhoi U K Misra Sanjay Gandhi Postgraduate Institute of Medical Sciences, Radiodiagnosis Lucknow- India ASNR 54 th 2016 Annual Meeting Presentation #: eP-78 Abstract Control Number 1785

2. Disclosure The authors have no disclosures to report.

3. Background Subacute combined degeneration (SACD) is the clinically manifestation of the B12 deficiency, characterized by sensory ataxia, spasticity and peripheral neuropathy. B12 deficiency results in myelin dysfunction which responds to cobalamine treatment (Kalita et al 2008; Misra et al 2003; Hammer et al 1998). Nutritional amblyopia is attributed to vitamin B12 deficiency. In more recent studies on vitamin B12 deficiency neurological syndrome (VBDNS) vision is seldom affected which may be attributed to early diagnosis and treatment (Healton et al 1991; Pandey et al 2004; Mishra et al 2007).

4. Background contd… Only one out of 57 patients of VBDNS was found with visual loss ( Mishra et al 2007 ). Optic nerve involvement has been reported in 1 out of 153 patients of VBDNS (Fine et al 1993), highlighting the rarity of visual impairment. Subclinical visual involvement as assessed by visual evoked potentials (VEP) has been reported in 58.8% of VBDNS patients (Pandey et al 2004). Diffusion tensor imaging (DTI) is a new technique for evaluating white matter changes measuring the water diffusivity.

5. Background contd… SACD is associated with high frequency of VEP abnormalities. DTI study of optic nerve may provide valuable information about the pathophysiology of subclinical visual evoked potential (VEP) abnormality in SACD. There is no study correlating DTI of optic nerve with VEP changes in the patients with SACD.

6. How DTI helps in Quantification Various DTI parameters quantifies the amount of nonrandom water diffusion within tissues and provides unique in vivo information about the pathological processes. Fractional Anisotropy (FA) - assesses the degree of directionality of diffusion ( anisotropic diffusion) at a particular region. Radial diffusivity (RD) - diffusion perpendicular to the main diffusion direction. Apparent diffusion coefficient (ADC) - independent of direction in a certain voxel. So degeneration or damage of white matter tracts is expected to result in reduced FA (loss of diffusion directionality) and the increase in ADC (loss of myelin and axonal membranes).

7. Purpose Subacute Combined degeneration is associated with high frequency of visual evoked potential abnormalities but there is no MR functional study on optic nerve. We assessed and correlated the functional integrity of optic nerves using diffusion tensor imaging (DTI) in patients with B12 deficiency and post therapy response.

8. Materials and Methods Inclusion criteria: Prospective evaluation of six patients (age range 14–59 years), male:female ratio (5:1). For validity of the study, six healthy controls ages (27 - 60 years), male:female ratio (5:1) were also included in the study Diagnosis of SACD – 1. Charecterstic clinical features 2. Low serum B12 levels (<211 pg/ml) and 3. Somatosensory and VEP changes. Exclusion criteria: The patients with history of stroke, structural brain lesion, hepatic/renal failure, seizures and toxic exposure were excluded. HIPPA compliant and granted permission by Research Ethics Board review.

9. Materials and Methods contd… Following investigations were done: 1. Fundus examination for optic atrophy and macular/retinal changes. 2. Fasting serum vitamin B12 level and 3. Pattern shift visual evoked potential (PSVEP). Latency and amplitude of P100 waveform values (abnormal ≥2.5 SD of normal). Upper limit of normal P100 latency = 106 (96.9 ± 3.6) ms Lower limit of amplitude = 3.0 (7.8 ± 1.9) mV (Misra and Kalita, 2013). Patients were treated with parenteral cobalamine 1000µg daily for 10days followed by weekly for 1 month and thereafter monthly. Patients were followed up at 3months and their clinical, VEP and DTI study were repeated.

10. Data acquisition, Data fusion and region of interest analysis MRI head and orbit was performed on a 3T magnetic resonance GE scanner (Signa HDxt; General Electric, Milwaukee, USA), using head, neck and spine coil. Routine imaging sequences of Head (T1,T2 FLAIR, T2 propeller, DWI) and Orbit (T1 and T2 with and without Fat suppression) were obtained. DTI of the bilateral optic nerves was done in pre, post- treatment and control group. (DTI sequence- single shot axial EPI sequence, b-1000 s/mm2, slice thickness 1.6 mm, interslice gap 0, FOV 24mm, voxel size of 1.09x1.09x1.6 mm, matrix 128x128 and 15 diffusion directions.

11. Patients were instructed to keep the eyes close and not to do ocular movements). DTI data analysed on FuncTool software – ADW4.4 GE workstation. After using a motion correction algorithm FA, ADC and structural diffusion tensor maps (Figure 1 ) were generated. Region of interest (ROI) measuring (≤14mm 2) in the mid- length of the intraorbital part of the visualised optic nerve.

12. Statistical analysis: Mann-Whitney u test was used to compare FA, AD, RD, MD and ADC values of optic nerve between patients and controls using Paired t test was used to compare the initial and 3month follow up DTI and VEP parameters (P100 latency and amplitude) were compared using. The baseline FA value was correlated with age, gender and duration of illness, and P100 latency and amplitude of VEP using Spearman and independent t test. Statistical analysis was done using SPSS 16 version software and the variable having a P value <0.05 was considered significant.

13. Results Median duration of illness - 1.75 (1.5- 36) months. MRI study: No signal changes in the optic nerve and brain parenchyma. Clinical symptoms No. of patients Sensory ataxia 6/6 peripheral neuropathy 3/6 cognitive abnormalitie s 1/6 visual abnormality 0/6 Visual testing Normal in all patients P100 latency of PSVEP Prolonged in 5/6 patients Amplitude of P100 Reduced in 1 /6 patients

14. Results contd… DTI Indices of Optic Nerves Patients (Pre- treatment) Control Group Mean FA value0.37-0.540.55-0.70 Mean RD value4.1-4.33.03-4.11 Mean FA value of the optic nerves was significantly reduced in the patients compared to control (P=0.008). Mean RD value of the optic nerves was significantly increased in the patients compared to the controls (P=0.002).

15. Results contd… DTI Indices of Optic Nerves Pre treatment Post treatment ControlP-Value (Pretreat ment versus control) P-Value (Pre versus post treatment ) P-Value (post treatment versus control) FA 0.498 +0.071 0.622+0. 062 0.632+0. 053 p=0.004p=0.008p=0.818 RD 4.217+0. 105 4.078+0. 158 4.058+0. 082 p=0.016p=0.002p=0.937 The mean ADC, MD and AD values were not different between the patients and the controls

16. Fig.1 Pre-treatment (a-c) and post Cobalamine treatment (d—f) DTI obtained in a 27- year-old man with subacute combined degeneration. (a) structural diffusion-tensor index, (b) apparent diffusion coefficient and (c) fractional anisotropy maps Regions of interest are placed in the middle part of both the optic nerve. a b c def

17. Figure-2: Visual evoked potential of the same patient revealed prolonged P100 latency on both right and left eye (126.9/121.8ms) which normalized (102.5/101.5ms) at 3 months after treatment.

18. Fig. 3 The error bar diagram shows normalization of FA and RD in the patients with subacute combined degeneration (SACD) 3 months after cobalamine treatment.

19. Correlation DTI indicesLab parameters R valueP value Mean FA value P100 latencyr=-0.81P=0.05 Mean FA value serum vitamin B12 level r=0.01P=0.91

20. Follow up at 3 months Clinical: All the patients improved. VEP and DTI: 1. P100 latency improved from baseline in all although it remained prolonged in 5 eyes ((111.76 + 9.01 Vs105.34 + 6.63 ms; P=0.02). 2. P100 amplitude however did not show significant change ((6.84±4.02 Vs6.44±3.20; P=0.55). The improvement in VEP paralleled with improvement in FA FA (0.50 ± 0.07 vs 0.62 + 0.07; P<0.001) and RD values (4.22 ± 0.11 vs 4.08 + 0.19; P=0.04) at 3 months.

21. Summary Subclinical optic nerve dysfunction in SACD patients was evident on DTI and VEP studies. DTI study of optic nerve revealed reduced FA and increased RD values compared to the controls. FA value in the patients correlated with P100 latency but not with amplitude. Cobalamine treatment for 3months resulted normalization of FA value and improvement in P100 latency. The normal conventional MRI of optic nerve and visual testing with reduced FA on DTI and prolongation of P100 latency are consistent with myelin dysfunction. This is the first study in the patients with SACD reporting the DTI changes in optic nerve and correlated these changes with VEP findings.

22. Limitations 1.Small sample size. 2.Performing DTI study of optic nerve is technically difficult because of small size and is susceptible for arterial and venous pulsations.

23. Conclusion DTI and VEP studies confirm the subclinical myelin dysfunction of optic nerve in the patients with SACD which improves following cobalamine treatment.