Atypical presentation of Charcot–Marie–Tooth disease 1A: A case report

Adolescent Onset of Muscle Weakness

Pediatric adolescent muscle weakness can be from a variety of causes. Methodical diagnostic evaluation can lead to the category of diseases whereby phenotypic overlap requires either specialized care or broad testing patterns. However, having the ultimate diagnosis is important for prognostication.

Review of general and head and neck/oral and maxillofacial features of Charcot-Marie-Tooth disease and dental management considerations

Charcot-Marie-Tooth disease (CMTD) is an uncommon progressive neuromuscular disorder of the peripheral nervous system and primarily leads to distal extremity weakness and sensory deficits. Frequently, affected patients manifest pes cavus, drop foot, and digit contractures that may pose significant challenges in ambulation and grasping objects. Although there are numerous articles of this syndrome in the medical literature, there is a limited number of dental publications. The objective of this article is to review the general and head and neck/oral and maxillofacial features of CMTD. General guidelines for dental management are also provided.

New evidence for secondary axonal degeneration in demyelinating neuropathies

Development of peripheral nervous system (PNS) myelin involves a coordinated series of events between growing axons and the Schwann cell (SC) progenitors that will eventually ensheath them. Myelin sheaths have evolved out of necessity to maintain rapid impulse propagation while accounting for body space constraints. However, myelinating SCs perform additional critical functions that are required to preserve axonal integrity including mitigating energy consumption by establishing the nodal architecture, regulating axon caliber by organizing axonal cytoskeleton networks, providing trophic and potentially metabolic support, possibly supplying genetic translation materials and protecting axons from toxic insults. The intermediate steps between the loss of these functions and the initiation of axon degeneration are unknown but the importance of these processes provides insightful clues. Prevalent demyelinating diseases of the PNS include the inherited neuropathies Charcot-Marie-Tooth Disease, Type 1 (CMT1) and Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) and the inflammatory diseases Acute Inflammatory Demyelinating Polyneuropathy (AIDP) and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP). Secondary axon degeneration is a common feature of demyelinating neuropathies and this process is often correlated with clinical deficits and long-lasting disability in patients. There is abundant electrophysiological and histological evidence for secondary axon degeneration in patients and rodent models of PNS demyelinating diseases. Fully understanding the involvement of secondary axon degeneration in these diseases is essential for expanding our knowledge of disease pathogenesis and prognosis, which will be essential for developing novel therapeutic strategies.

Prevalence and significance of cranial nerve imaging abnormalities in patients with hereditary neuropathies: Clinical implications at the skull base

OBJECTIVE

To estimate the prevalence and significance of cranial nerve (CN) imaging abnormalities in patients with hereditary neuropathy and discuss clinical implications.

METHODS

We retrospectively analyzed data from patients at four tertiary academic medical centers with hereditary neuropathy diagnoses who had undergone gadolinium-enhanced magnetic resonance imaging (MRI) of the brain or skull base between 2004 and 2018. MRI scans, as well as computed tomography imaging when available, were reviewed and bivariable analysis was performed to identify predictors of CN abnormalities on imaging.

RESULTS

Among 39 patients meeting study criteria, 11 had clinical CN deficits (28%) and 8 had CN abnormalities on imaging (21%). Of the patients with CN abnormalities on imaging, half had CN deficits (4/8) and only a quarter had imaging abnormalities of the CNs with the deficits (2/8). Imaging abnormalities were found in varied CNs, including CNs III, V, VII, and the VII/VIII complex in the internal auditory canal. MRI obtained for the purpose of evaluating CN deficits had a statistically significant increased likelihood of containing CN imaging abnormalities. However, CN deficits themselves were not predictive of imaging abnormalities.

CONCLUSION

Thickening and enhancement of CNs on MRI may be found in approximately 1/5 of patients with hereditary neuropathies and are inconsistently associated with clinical deficits. These imaging findings should not be mistaken for neoplastic and infectious processes as they may be manifestations of the patients' underlying genetic neuropathy.

LEVEL OF EVIDENCE

4.

A novel mutation in FGD4 causes Charcot-Marie-Tooth disease type 4H with cranial nerve involvement

Charcot-Marie-Tooth disease type 4H (CMT4H) is a rare variant of autosomal recessive hereditary neuropathy. It is caused by FGD4 mutations and characterized by early infantile onset, slowly progressive distal muscle weakness, scoliosis, and myelin outfoldings visible in nerve biopsy samples. Here, we report a 65-year-old male born to consanguineous parents, who carries a novel homozygous FGD4 c.724C>T nonsense mutation. He developed lower limb weakness in his teens, which progressed slowly and was accompanied by diplopia, bilateral hearing loss, and erectile dysfunction from his twenties. At the age of 65, he was wheelchair-bound and had mild scoliosis, bilateral ophthalmoplegia, facial muscle weakness, inner ear hearing loss, distal-dominant weakness, and sensory disturbance, but no cognitive deterioration. Magnetic resonance imaging revealed enlarged bilateral trigeminal and facial nerves. Accordingly, we believe that this mutation causes slowly progressive sensorimotor neuropathy with apparent cranial nerve involvement, thereby further expanding the clinical spectrum of CMT4H.