Understanding ALS

Diagnosis of ALS

The first responsibility of a physician caring for a patient with ALS is to be certain of the diagnosis. Unfortunately, ALS is a clinical diagnosis, and no diagnostic test assures diagnostic certainty. Our clinical criteria require evidence of weakness, wasting, and fasciculations (lower motor neuron signs) in combination with Babinski signs or clonus (upper motor neuron signs). Sensation is spared clinically, but morphological and physiological studies may show minor changes. In patients who do not have Babinski sign or clonus but have incongruously active reflexes in weak, wasted, and fasciculating limbs, we use the term ALS with probable upper motor neuron signs (PUMNS). If there are only lower motor neuron signs, the term is progressive muscular atrophy (PMA), and if there are only upper motor neuron signs, it is called primary lateral sclerosis (PLS). Clinical findings that exclude the diagnosis of ALS include persistent and unexplained sensory loss, dysfunction of bladder or bowel, and involvement of ocular muscles (which may occur late). Because ALS develops so gradually, the disease has often progressed 20-50 percent by the time a diagnosis is confirmed.

The diagnostic process consists of the patient's full medical history and a physical and neurological examination repeated at regular intervals to observe any progression. The following tests may also be administered to rule out other diagnoses that may mimic ALS:

• Electromyogram (EMG) - a test that detects electrical activity in the muscles.
• Nerve Conduction Velocity (NCV) - tests the nerve to rule out other neurological disorders such as peripheral neuropathy or myopathy.
• Magnetic Resonance Imaging (MRI) - a procedure that is non-invasive and that uses a magnetic field to produce high quality images of the brain and spinal cord.
• Blood Tests - to assess the presence of heavy metals in the blood; CPK to rule out muscle disease (CPK is normal in ALS); Lyme titers or western blot, B12, Anti-GM1 antibody titers, and serum protein electrophoresis can also be ordered to rule out diseases that can mimic ALS.
• Lumbar Puncture - (LP) is an invasive diagnostic test, in which CSF (cerebrospinal fluid) is extracted and analyzed for any abnormalities.
• Muscle Biopsy - A procedure involving removal and examination of a piece of muscle tissue. This test is not routinely performed, but is indicated in cases where the diagnosis is tricky.