Differential diagnosis can be challenging due to the number of overlapping symptoms, shared between several<unk> s. Frequently, the diagnosis is based on clinical findings (i.e. LMN vs. UMN signs and symptoms, patterns of weakness), family history of<unk> , and a variation of tests, many of which are used to rule out disease mimics, which can manifest with identical symptoms. Classification Corticospinal tract. Upper<unk>  neurons originating in the primary<unk>  cortex synapse to either lower<unk>  neurons in the anterior horn of the central gray matter of the spinal cord (insert) or brainstem<unk>  neurons (not shown).<unk>  can affect either upper<unk>  neurons (UMNs) or lower<unk>  neurons (LMNs).<unk>  describes a collection of clinical disorders, characterized by progressive muscle weakness and the degeneration of the<unk>  neuron on electrophysiological testing. As discussed above, the term<unk> " has varying meanings in different countries. Similarly, the literature inconsistently classifies which degenerative<unk>  neuron disorders can be included under the umbrella term<unk> ". The four main types of<unk>  are marked (*) in the table below. All types of<unk>  can be differentiated by two defining characteristics: # Is the disease sporadic or inherited? # Is there involvement of the upper<unk>  neurons (UMN), the lower<unk>  neurons (LMN), or both? Sporadic or acquired<unk> s occur in patients with no family history of degenerative<unk> . Inherited or genetic<unk> s adhere to one of the following inheritance patterns: autosomal dominant, autosomal recessive, or X-linked. Some disorders, like ALS, can occur sporadically (85%) or can have a genetic cause (15%) with the same clinical symptoms and progression of disease. UMNs are<unk>  neurons that project from the cortex down to the brainstem or spinal cord. LMNs originate in the anterior horns of the spinal cord and synapse on peripheral muscles. Both<unk>  neurons are necessary for the strong contraction of a muscle, but damage to an UMN can be distinguished from damage to a LMN by physical exam. Type UMN degeneration LMN degeneration Sporadic<unk> s Sporadic amyotrophic lateral sclerosis (ALS)* Yes Yes Primary lateral sclerosis (PLS)* Yes No Progressive muscular atrophy (PMA)* No Yes Progressive bulbar palsy (PBP)* Yes Yes, bulbar region Pseudobulbar palsy Yes, bulbar region No Monomelic amyotrophy (MMA) No Yes Inherited<unk> s Familial amyotrophic lateral sclerosis (ALS)* Yes Yes Tests * Cerebrospinal fluid (CSF) tests: Analysis of the fluid from around the brain and spinal cord could reveal signs of an infection or inflammation. * Magnetic resonance imaging (MRI): An MRI of the brain and spinal cord is recommended in patients with UMN signs and symptoms to explore other causes, such as a tumor, inflammation, or lack of blood supply (stroke). * Electromyogram (EMG) & nerve conduction study (NCS): The EMG, which evaluates muscle function, and NCS, which evaluates nerve function, are performed together in patients with LMN signs. * For patients with<unk>  affecting the LMNs, the EMG will show evidence of: (1) acute denervation, which is ongoing as<unk>  neurons degenerate, and (2) chronic denervation and reinnervation of the muscle, as the remaining<unk>  neurons attempt to fill in for lost<unk>  neurons. * By contrast, the NCS in these patients is usually normal. It can show a low compound muscle action potential (CMAP), which results from the loss of<unk>  neurons, but the sensory neurons should remain unaffected. * Tissue biopsy: Taking a small sample of a muscle or nerve may be necessary if the EMG/NCS is not specific enough to rule out other causes of progressive muscle weakness, but it is rarely used.
Motor neuron disease
Vascular myelopathy
Polyneuropathy
Basal ganglia disease
Upper motor neuron syndrome
Distal hereditary motor neuronopathies
Tropical ataxic neuropathy
Amyotrophic lateral sclerosis