Neurofilaments can differentiate ALS subgroups and ALS from common diagnostic mimics.

Delayed diagnosis and misdiagnosis are frequent in people with amyotrophic lateral sclerosis (ALS), the most common form of motor neuron disease (MND). Neurofilament light chain (NFL) and phosphorylated neurofilament heavy chain (pNFH) are elevated in ALS patients. We retrospectively quantified cerebrospinal fluid (CSF) NFL, CSF pNFH and plasma NFL in stored samples that were collected at the diagnostic work-up of ALS patients (n = 234), ALS mimics (n = 44) and controls (n = 9). We assessed the diagnostic performance, prognostication value and relationship to the site of onset and genotype. CSF NFL, CSF pNFH and plasma NFL levels were significantly increased in ALS patients compared to patients with neuropathies & myelopathies, patients with myopathies and controls. Furthermore, CSF pNFH and plasma NFL levels were significantly higher in ALS patients than in patients with other MNDs. Bulbar onset ALS patients had significantly higher plasma NFL levels than spinal onset ALS patients. ALS patients with C9orf72HRE mutations had significantly higher plasma NFL levels than patients with SOD1 mutations. Survival was negatively correlated with all three biomarkers. Receiver operating characteristics showed the highest area under the curve for CSF pNFH for differentiating ALS from ALS mimics and for plasma NFL for estimating ALS short and long survival. All three biomarkers have diagnostic value in differentiating ALS from clinically relevant ALS mimics. Plasma NFL levels can be used to differentiate between clinical and genetic ALS subgroups.

Impact of Amyotrophic Lateral Sclerosis on Slow Tonic Myofiber Composition in Human Extraocular Muscles.

Purpose: To analyze the proportion and cross-sectional area of myofibers containing myosin heavy chain slow-twitch (MyHCI) and myosin heavy chain slow tonic (MyHCsto) in extraocular muscles of autopsied amyotrophic lateral sclerosis (ALS) patients with either spinal or bulbar site of disease onset. Methods: Whole-muscle cross sections from the middle portion of the medial rectus were labeled with antibodies against MyHCI or MyHCsto and laminin. Myofibers labeled with the MyHC antibodies (MyHCI+sto) and the total number of myofibers were quantified in the orbital and global layer of 6 control individuals and 18 ALS patients. The cross-sectional area of myofibers labeled for either MyHC was quantified in 130 to 472 fibers/individual in the orbital and in 180 to 573 fibers/individual in the global layer of each specimen. Results: The proportion of MyHCI+sto myofibers was significantly smaller in the orbital and global layer of ALS compared to control individuals. MyHCI+sto myofibers were significantly smaller in the global layer than in the orbital layer of ALS, whereas they were of similar size in control subjects. The decreased proportion of MyHCI+sto fibers correlated significantly with the age of death, but not disease duration, in patients who had the bulbar-onset variant of ALS but not in patients with spinal variant. Conclusions: ALS, regardless of site of onset, involves a loss of myofibers containing MyHCI+sto. Only in bulbar-onset cases did aging seem to play a role in the pathophysiological processes underlying the loss of MyHCI+sto fibers.

Pax7-Positive Cells/Satellite Cells in Human Extraocular Muscles.

PURPOSE: We quantified and investigated the distribution of Pax7-positive cells/satellite cells (SCs) in the human extraocular muscles (EOMs). METHODS: An immunofluorescence multiple-marker method simultaneously combining two SC markers (Pax7, NCAM), detection of the basement membrane (laminin) and cell nuclei (4',6-diamidino-2-phenylindole [DAPI]), was used on the anterior, middle, and posterior portions of EOMs from five healthy donors. Pax7-positive cell and SC content, myonuclear content, myofiber cross-sectional area, and myonuclear domain were analyzed in single cross-sections. Between 3915 and 13,536 myofibers per muscle cross-section and myofibers from the entire EOM cross-section were analyzed for quantification of Pax7-positive cells per myofiber (Pax7/F). RESULTS: The number of Pax7/F in the human EOMs varies along the length of the muscle with twice as high Pax7/F in the anterior part of the EOMs, but within the range of what has been previously reported for normal adult limb muscles. Furthermore, there are Pax7-positive cells in positions other than the classical SC position and the myonuclear domain size of adult EOMs is noticeably smaller than that previously reported for other adult skeletal muscles. CONCLUSIONS: Previous data on differences in Pax7-positive cell/SC abundance between EOMs and limb muscles must be reconsidered and the characteristics of different Pax7-positive cell populations further investigated. Higher numbers of Pax7-positive cells in the anterior portion of the EOMs may have a bearing for strabismus surgery involving sectioning of the muscle fibers.

Unaffected motor endplate occupancy in eye muscles of ALS G93A mouse model.

Amyotrophic lateral sclerosis (ALS) is a progressive, lethal neurodegenerative disorder characterised by selective loss of motor neurons with accompanying muscle paralysis and respiratory failure. Despite progressive paralysis in trunk and extremity muscles, disturbed eye motility is not a hallmark of ALS. Extraocular muscles (EOMs) of terminal ALS patients show far less morphological signs of disease than their limb muscles. One of the earliest signs of the disease in the transgenic G93A SOD1 mouse model of ALS is loss of motor neuron contact at the neuromuscular junctions (NMJ) in limb muscles. We used immunohistochemistry to identify NMJs and evaluate innervation in EOMs and limb muscles of G93A mice. In G93A limb muscles, loss of axonal contact was seen in 6-82 percent of the NMJs. On the contrary, the degree of endplate occupancy in the EOMs did not differ between transgenic mice and wild-type controls. We propose that EOM-specific properties make these muscles more resistant to the underlying pathophysiological process of ALS and that the EOMs are a useful model to advance our understanding of ALS.