B12 Deficiency case study (Dr. Mahoney)

Question 1

Romberg’s Test

Answer 1

• Detects inability to maintain a steady standing posture.

- Positive test is excessive swaying with the eyes closed but NOT open.

Question 2

With eyes open, 3 sensory systems provide input to the cerebellum to maintain

Answer 2

Truncal stability: vision, proprioception, and vestibular sense (CN VIII)

Question 3

Mild lesion in vestibular or proprioception systems can usually be compensated for with:

Answer 3

eyes opened, but not in cerebellum. Thus with eyes closed, visual input removed and instability can be brought out.

Question 4

Severe vestibular or proprioceptive lesion, or mild line cerebellar lesion leads to:

Answer 4

patient being unable to maintain balance even with eyes opened or closed.

Question 5

Peripheral Neuropathy Symptoms

Answer 5

Includes sensory, motor, or autonomic nerve pathology alone or in combination with each other.

Question 6

Diseases that cause peripheral neuropathy

Answer 6

Diabetes mellitus, AIDS, thyroid disease, alcoholism, vitamin deficiencies (B12), renal failure, cancer, chemotherapy, drugs, chemicals, and toxins.

Question 7

Pernicious Anemia

Answer 7

• Most common cause of B12 deficiency.
• Lack of intrinsic factor; necessary for B12 absorption by the duodenum.
• Leads to B12 deficiency.
• Not that common.

Question 8

Food-Cobalamin Malabsorption

Answer 8

Gastric mucosa may atrophy with age, and thus stop producing IF or autoantibodies may attack parietal cells.
* More common than pernicious anemia.

Question 9

B12 Deficiency

Answer 9

Leads to a defect in DNA synthesis, especially in cells with rapid turnover, like blood cells, which can lead to anemia.
- Also impairment to myelin sheath of nerves.

Question 10

Vitamin B12

Answer 10

• Important cofactor in the conversion of homocysteince to methionine.
• Methionine needed for production of choline-containing phospholipids which are formed in the myelin sheath of nerves.

Question 11

Subacute combined degeneration of the spinal column

Answer 11

• Caused by B12 deficiency.
• Affects the posterior and lateral spinal columns of spinal cord.
• Posterior column transmits vibration and position sense.
• Lateral coordinates voluntary movement. Disorders cause stroke-like symptoms.

Question 12

Megaloblastic Anemia

Answer 12

• Caused by defective RBC production leading to fewer cells formed.
• Those RBCs that form are larger and have more pigment.
• Indirect bilirubin increase due to increased RBC fragility.
• Bone marrow hyperplastic.

Question 13

Treatment of B12 Deficiency

Answer 13

• Life-long B12 supplementation.
• In form of monthly IM injections.
• Or daily oral crystalline B12 at dose 200x normal.
• Oral is still effective because 1-5% of cobalamin is absorbed pasisively, without intrinsic factor. Hence the high dose.