Electromyogram and nerve conduction in patients with acute intermittent porphyria

Abstract

Diminished activity of uroporphyrinogen I-synthetase in the liver and other tissues may be regarded to be the primary genetic deficiency of acute intermittent porphyria (AIP). Increased production and renal excretion of delta-aminolevulinic acid (ALA) und porphobilinogen (PBG) are secondary phenomena. The neuropsychiatric symptomatology of AIP consists of neuropathy, vegetative crises and exogenous psychoses. In this study electromyographic and neurographic investigations were performed on 20 persons with AIP. 16 patients had experienced attacks of AIP, 10 of them including neuropathy. 4 persons showed the biochemical findings of AIP but had not yet had symptoms. In cases with persistent pareses following porphyric neuropathy denervation signs or sequelae were still present. In patients without clinical symptoms and in latent cases there were normal or borderline findings. Motor nerve conduction velocity was mostly decreased in combination with denervation signs and in a range that indicated a primarily axonal nerve lesion and consequent myelin damage rather than primary demyelinization. The mean motor conduction velocity of n. tibialis was somewhat lower in patients with porphyric crises without neuropathy than in latent cases without any clinical crises. The differences were not significant in other nerves. The findings are discussed under consideration of the electrodiagnostic results of other investigations and of neuropathological and clinical data.

Motor neuropathy in porphobilinogen deaminase–deficient mice imitates the peripheral neuropathy of human acute porphyria

“…The results of these nerve conduction studies in PBGD -/-mice are consistent with electrophysiological findings in patients with porphyric neuropathy who suffer from an axonal neuropathy that predominantly affects motor fibers with little electrophysiological evidence of demyelination (6,(20)(21)(22). EMG findings in human porphyric neuropathy usually reveal decreased recruitment of MUAPs shortly after onset of weakness, with pathological spontaneous activity first appearing in proximal muscles and later spreading to distal muscles (20,21).…”

“…The increase of MUAP amplitudes also is consistent with enlargement of motor unit size due to reinnervation, as is the observation of axonal growth cones and axonal sprouts (Figure 3, c and d). Electromyographic findings in human porphyric neuropathy usually also reveal decreased recruitment of MUAPs shortly after onset of weakness (20,21).…”

Porphyric neuropathy: a clinical, neurophysiological and morphological study

“…In effect, we observed a case of acute neuropathy with practically total denervation in the proximal muscles and a near-normal motor and sensory conduction velocity. This dissociation is regarded as fairly typical of primary axonal damage [7,18]. Our morphological data argue the same way: we found no evidence of segmental demyelination and demonstrated conservation of the linear ratio of fiber diameter to internodal distance, which tells against the presence of significant demyelination-remyelination processes [13].…”

Light‐microscopic and microspectrofluorometric characterization of porphyrin‐containing astrocytes in mouse optic nerve

“…The effects of ALA on the optic nerve or other cranial and peripheral nerves are little known (Flugel and Druschky, 1977). However, ALA may impair propagation of electrical impulses in nerves (Sima et al, 1981).…”