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Motor Neuron Disease – another opinion

Short summary

72-year-old female developed progressive dysarthria and dysphagia. Her doctor describes her speech difficulty as “Spastic dysarthria with slow and nasal speech" and noticed decreased mobility in the tongue and palate. She underwent multiple investigations and started Rilutek. Since there is no biologic marker for ALS, the expert suggests further testing that is focused on trying to rule out other disorders and show diffuse lower motor neuron involvement

Patient's questions

The patient asks about the diagnosis and about other recommended investigations in order to establish the diagnosis.

Medical Background

Diagnosis: motor neuron disease.

The patient is a 71 year old lady who developed progressive speaking difficulties since June of 2008. More recently, she developed progressive swallowing difficulties as well.

In December of 2008 was seen by Dr. X, neurology specialist in Milan. He describes her speech difficulty as “Spastic dysarthria with slow and nasal speech”. He notices decreased mobility in the tongue and palate with no other neurological signs on exam.

Multiple investigations including blood work, brain MRI and electro diagnostic studies were performed, the results are summarized below.

Rilutek 50 mg twice a day was started on January 2009.

Previous investigations:

- Blood work: Complete blood count, chemistry, glucose, CK levels, liver function tests, thyroid function tests, serum protein electrophoresis (SPEP) were all within normal limits. SPEP with immunofixation was performed, but the report is unclear.

- Brain MRI (1/2008) revealed evidence of cortical cerebral atrophy with possible periventricular white matter changes. There were no other intracranial lesions. The actual MRI images were not available for review.

- EMG (French) in January 2009: Nerve conduction studies revealed bilateral median neuropathy across the wrists, worse on the left. Ulnar sensory and motor responses were within normal limits on both sides. Tibial nerve motor responses were within normal limits on both sides. F-wave responses of right and left ulnar and tibial nerves were within normal limits. Repetitive nerve stimulation of the left spinal accessory and right facial nerves were within normal limits. Single fiber EMG was normal. Needle EMG study revealed abnormal spontaneous activity in the left orbicularis oris, right FDI and right biceps. It also revealed evidence of chronic denervation in the right and left tibialis anterior. Left FDI and Glossus muscles were normal.

- Transcranial magnetic stimulation (French) in January 2009: within normal limits.

Past medical and family history is not available.

Social and occupational history is not available.

Current list of medication is not available.

Medical opinion

It must be noted that not infrequently early in the course of ALS it is not possible to come to a definite diagnosis. As noted below, there is no
biologic marker for ALS, so testing is focused on trying to rule out other disorders and show diffuse lower motor neuron involvement
. I have added some additional tests that address both of these suggestions but it is likely that her current physicians may be correct at the present time.

The records which I received, suggests that the patient is about 72 and has had spastic dysarthria with recent dysphagia over the past 6 months. There are not reported imaging abnormalities of the posterior fossa. EMG and NCV studies did not show electrophysiologic evidence for ALS or neuromuscular junction defect. Pulmonary function tests including routine spirometry as well as maximal inspiratory and expiratory pressure testing can be useful to identify subtle pulmonary muscle involvement. Swallowing evaluation may also help delineate the nature of her dysphagia ( liquids more than solids?).

It seems that the physicians who are caring for the patient have ordered the correct tests. I would add some additional details as outlined below. Since there is no biologic marker for ALS it is a diagnosis of exclusion. Meaning other treatable disorders must be ruled out. About 20% of cases of ALS present with symptoms isolated to the bulbar region, making it difficult to arrive at a presumptive diagnosis. It is unclear if there are fluctuations in clinical symptoms during the course of the day which might suggest Myasthenia Gravis despite the normal decrement and SFEMG. Antibodies to acetylcholine receptor antibodies including MUSK would be helpful. Additional details about extremity motor, sensory and reflex exam would be useful to identify whether there is a mixed picture of upper and lower motor neuron dysfunction. In addition, more extensive cognitive testing and assessment of the extramyramidal system would be helpful to rule out other classes of neurodegerative disorders that can co-exist with bulbar dysfunction, particularly spastic.

While EMG /NCV may be unremarkable at early stages, sufficient sampling of extremity muscles i.e. three limbs plus paraspinal muscles is necessary to assess whether there is sufficient diffuse active neurogenic changes i.e. positive and fibrillation potentials. Sometime lumbar puncture and muscle biopsy can be useful to rule out confounders of motor neuron disorders and we could consider it after the above testing if non-diagnostic.

I have included a list of blood tests that may be helpful and do not need to be repeated if already done: SMA-18, CBC with platelets, B12 & folate, thyroid function, ESR, CRP, ANA, ANCA, antiDNA, complements; VDRL., HIV, RF, homocysteine, fasting blood sugar, HbA1C, lipid profile, PTH level, calcium and magnesium, serum protein electrophoresis with immunofixation to rule out a monoclonal gammopathy; hexoseaminidase A, (adult onset Tay-Sach); anti-ganglioside anitibody (seen in multi-focal motor neuropathy). Antibody for anti-acetylcholineesterase and MUSK. I do not usually use Rilotek prior to finishing all of the above testing and as noted in the referral given the implications of the diagnosis suggest full testing to be sure that nothing is
inadvertently missed.