Motor neurone disease

A 66-year-old woman complains of stiffness and weakness climbing stairs. She has a history of hypertension and diet-controlled type 2 diabetes. On examination, there is mild upper arm weakness, hip flexion is 4−/5 bilaterally, with bilateral wasting and flickers of fasciculations in the right quadriceps. Knee extension is 4/5. Dorsiflexion and plantar flexion are strong. Brisk knee and ankle reflexes are elicited, as well as a positive Hoffman’s and Babinski’s sign. Sensory examination and cranial nerves are normal. Her BM is 8.9, her pulse is regular and her blood pressure is 178/97. What is the most likely diagnosis?

A. Myasthenia gravis

B. Diabetic neuropathy

C. Myositis

D. Motor neurone disease

E. Multiple sclerosis (MS)

 

Ans: Motor neurone disease

1 D This woman presents with upper (brisk reflexes, upgoing plantar) and lower (fasciculations) motor neurone signs. Motor neurone disease (MND) (D) presents with mixed upper and lower motor neurone signs and importantly no sensory involvement. In this case, there is involvement of two regions (arms and legs). Bulbar signs, such as tongue wasting and fasciculation, often help make the diagnosis. Myositis (C) affects the muscle, resulting in tenderness, wasting and fasciculation but no upper motor neurone (UMN) signs. Although the patient is diabetic, neuropathies (B) result in lower motor neurone (LMN) signs only. These may be motor and/or sensory. Typically, diabetes results in a peripheral neuropathy, most commonly sensory. The proximal distribution of weakness would be in keeping with myasthenia (A), but not the UMN signs. There is no mention of fatigability, which is a key feature. MS (E) in this age group is less common and an inflammatory disorder of the central nervous system would not result in LMN signs.

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