Primary non-Hodgkin lymphoma of the skull base presenting with Garcin syndrome: MRI manifestations.

Primary non-Hodgkin lymphoma of the skull base is a rare disorder. We report a case of primary non-Hodgkin lymphoma of the skull base presenting with Garcin syndrome. MRI revealed peculiar lesions in the cavernous sinus, clivus, and occipital bone. Diagnosis was made by biopsy of the tumor in the cavernous sinus.

Patterns of nerve conduction abnormalities in severe carpal tunnel syndrome.

Nerve conduction study findings in severe carpal tunnel syndrome have seldom been systematically investigated. The authors determined the persistence of each nerve conduction study parameter in severe carpal tunnel syndrome. Subjects were prospectively-collected 30 hands from 23 carpal tunnel syndrome patients, with an orthodromic sensory nerve action potential (SNAP) amplitude of the median nerve of 1 muV or less, or with an compound muscle action potentials (CMAPs) of the abductor pollicis brevis (APB) of 2 mV or less. Compound muscle action potentials of APB and second lumbricalis (2L) and orthodromic and antidromic SNAPs at the index finger were measured. As results, 2L-CMAP was obtainable for all but one hand, APB-CMAP for 20, orthodromic SNAP for 18, and antidromic SNAP for 13 hands. Four hands with preserved APB-CMAPs lacked SNAPs, whereas three hands with preserved orthodromic or antidromic SNAPs lacked APB-CMAPs. The mixed-nerve action potential at the wrist following orthodromic palm stimulation was identified in only 3 of 18 hands investigated. Orthodromic SNAP has an advantage that contamination by CMAPs is entirely lacking, and the authors documented its much higher persistence than previous studies because of their more detailed methods. Such different criteria of no response of SNAP between researchers should be taken notice in the grading system of carpal tunnel syndrome.

Mitochondrial GTPase mitofusin 2 mutation in Charcot-Marie-Tooth neuropathy type 2A.

Charcot-Marie-Tooth disease (CMT) has been classified into two types, CMT1 and CMT2, demyelinating and axonal forms, respectively. CMT2 has been further subdivided into eight groups by linkage studies. CMT2A is linked to chromosome 1p35-p36 and mutation in the kinesin family member 1B-beta (KIF1B) gene had been reported in one pedigree. However, no mutation in KIF1B was detected in other pedigrees with CMT2A and the mutations in the mitochondrial fusion protein mitofusin 2 (MFN2) gene were recently detected in those pedigrees. MFN2, a mitochondrial transmembrane GTPase, regulates the mitochondrial network architecture by fusion of mitochondria. We studied MFN2 in 81 Japanese patients with axonal or unclassified CMT and detected seven mutations in seven unrelated patients. Six of them were novel and one of them was a de novo mutation. Most mutations locate within or immediately upstream of the GTPase domain or within two coiled-coil domains, which are critical for the functioning or mitochondrial targeting of MFN2. Formation of a mitochondrial network would be required to maintain the functional peripheral nerve axon.