Subacute Combined Degeneration of the Cord

Paresthesias • Xray of the Week 2016 • Week #42

This 60 year old caucasian male with stage 4 fibrosis of liver presented with unsteady gait and falls. He also had paresthesias including tingling and numbness of the wrists for one month.

Laboratory values as follows:

MMA = 24,600 (N 0-0.40 nmol/mL)

B12 = 142 (N= 150 to 350 pg/mL.)

Folate = 14.5 (N= 2-20 ng/mL)

Hgb = 12.8 (N= 13-17 g/dL)

MCV = 129 (N= 80-100 fL)

MRI of cervical spine was done after the patient fell. What is the diagnosis?

Figure 1.: Axial and sagittal T2-weighted images showing dorsal column T2 hyperintensity suspicious for subacute combined degeneration of the cord.

In vitamin B12 deficiency, the methylmalonic acid (MMA) level may be elevated before the vitamin B12 level is low [1]. Elevated mean corpuscular volume (MCV) is a sign of B12 or folate deficiency, resulting in macrocytic anemia. This patient's markedly elevated MMA, low B12, and normal folate levels are diagnostic of vitamin B12 deficiency. Subacute combined degeneration of the cord is a metabolic disorder due to vitamin B12 deficiency which results in paresthesias of the hands and feet. Later in the disease, patients develop unsteady gait and weakness due to damage of the sensory tracts in the spinal cord[2]. The classic MRI appearance is abnormal high signal on T2 weighted images in the dorsal columns as well as lateral columns on T2-weighted images, leading to the "inverted V sign" [3-6]. Rarely the anterior columns may be involved [8]. The clinical symptoms and imaging findings are reversible with administration of vitamin B12 [2].

References:

1. How do we evaluate a marginally low B12 level? http://www.mdedge.com/jfponline/article/62530/how-do-we-evaluate-marginally-low-b12-level

2. Patten John P. Neurological Differential Diagnosis. Second Edition. London: Springer-Verlag, 1996. pg 234-235, Print.

3. Ravina B, Loevner LA, Bank W. MR findings in subacute combined degeneration of the spinal cord: a case of reversible cervical myelopathy. AJR Am J Roentgenol. 2000;174 (3): 863-5.

4. Kumar, Ashok, and Amar Kumar Singh. "Teaching NeuroImage: Inverted V sign in subacute combined degeneration of spinal cord." Neurology 72.1 (2009): e4-e4.

5. Naidich M, Ho S. Case 87: Diagnosis Please - Subacute Combined Degeneration. Radiology 2005; 237:101–105

6. Narra R, Mandapalli A, Jukuri N, Guddanti P. “Inverted V sign” in Sub-Acute Combined Degeneration of Cord. J Clin Diagn Res. 2015 May; 9(5)

7. Ketonen, Leena. Pediatric Brain and Spine: An Atlas of MRI and Spectroscopy. Berlin: Springer, 2005. pg 435, Print.

8. Karantanas AH, Markonis A, Bisbiyiannis G. Subacute combined degeneration of the spinal cord with involvement of the anterior columns: a new MRI finding. Neuroradiology. 2000;42 (2): 115-7.

Danielle Rice, MD is a neurohospitalist at Gottlieb Memorial Hospital, a part of Loyola University Health System. Dr. Rice graduated cum laude from Kent State University and earned her medical degree from Northeastern Ohio Universities College of Medicine. Dr. Rice completed a residency in adult neurology from Rush University Medical Center and a fellowship in multiple sclerosis from the University of Chicago. Dr. Rice is board certified in Neurology and is an assistant professor in the Department of Neurology of Loyola University Chicago Stritch School of Medicine.

Kevin Rice, MD is president of Global Radiology CME.

Follow Dr. Kevin Rice on Twitter @KevinRiceMD

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