In the group of paralyses due to neuritis, the influenza polyneuritis, the analogue of diphtheric paralysis, and that following other acute infectious diseases,-that is, a multiple degenerative neuritis,- is of chief importance. It is regarded as being due to the action of the specific toxins. The clinical picture varies with the distribution and extent of the nerve tracts affected. Thus a fulminant polyneuritis may produce the complete clinical picture of an acute ascending, so called Landry's paralysis, as in the cases described by Kahler and Eisenlohr. Neuritis of the extremities, especially of the lower extremities, sometimes leads to marked ataxia. This is the same curable acute "neuritic ataxia" of Strumpell which occurs occasionally in the course of other acute infectious diseases.
The prognosis of influenza polyneuritis appears to be better than that due to diphtheria; so far as I am aware, there is no published case in which the neuritis attacked the respiratory nerves and caused a fatal termination.
The numerous reports of cases show that polyneuritis due to influenza is no rare occurrence. We may mention the observations of Bidon, Brosset, Bruns, A. Church, Drasche, Holmberg, Homen, Jolly, Kahler, Krannhals, Leichtenstern, Leyden, Lojacone, Putnam, Remak, Ruhemann, Senator, Testi, Thue, Westphal.
The cases reported by Joffroy (see above), of paralysis due to neuritis, as also a case quoted by Bossers of paralysis of all four extremities, are remarkable inasmuch as the neuritis, besides affecting the motor tracts, also produced severe neuralgia in the sensory tracts. Remak* also notes in his case of polyneuritis the presence of "slight sensory disturbances."
Frequently influenza neuritis is localized to single nerves and thus produces isolated or grouped paralyses. There are numerous observations which must be interpreted as dependent upon neuritis. Other observations are probably to be explained as resulting from circumscribed, partial, functional, or degenerative changes due to the influence of a toxin in the motor nuclei of the middle and fourth ventricle-so called nuclear paralyses. This is especially the case in certain combined paralyses of the muscles of the eye, of the soft palate, and the pharynx, viz., muscle groups which, being synergic, are innervated from the same nuclei. The course of these paralyses was without exception favorable, consequently the observations on them are entirely clinical. They relate to clinical pictures which exhibit a kaleidoscopic variety. As regards the pathologic basis of these symptoms, whether neuritic or nuclear, whether functional or toxic, or due to inflammatory degenerative changes in the nerves or nuclei, there is no evidence. But one fact may be regarded as certain in all the cases belonging to this group, namely, that there cannot be gross pathologic changes; the complete absence of all severe cerebro bulbar or spinal symptoms in these cases at once negatives such a supposition.
The following observations may be cited from the large amount of available material.
We meet with numerous reports of paralysis of the soft palate and muscles of the pharynx, with or without simultaneous paralysis of accommodation. They are completely analogous to those paralyses which so frequently occur after diphtheria. However, the clinical pictures produced by influenza neuritis are much more varied as regards the arrangement of special muscle groups affected by the paralysis, whereas the diphtheric scheme is more even and uniform. Influenza affords a greater and more minute selection of individual nerves and nerve nuclei. Hence rare forms of paralyses occur-for instance, bilateral trochlear paralysis (Pfluger), isolated paralysis of the superior rectus (Vallude), etc. We may add the following observations: Isolated paralysis of the soft palate (Heymann); paralysis of accommodation with or without paralysis of the soft palate and muscles of the pharynx (Joachim, Jankau, Pfluger, Uhthoff, Albrand, Stower, Greff, Bergmeister, Sattler, Landolt, Frank, Guttmann, Bock, Neumann); intermittent paralysis of accommodation (Uhthoff); paresis of the internal rectus (Pfluger); weakness of the internal recti (Frank, Konigstein); paralysis of the superior rectus (Vallude); of both fourth nerves (Pfluger); of the third nerve (Fukala); of one or of both abducentes (Sattler, Coppez, van der Bergh); unilateral mydriasis (Lepine); bilateral paralysis of the third, fourth, and sixth nerves (Sattler, Pfluger); nuclear paralysis of the muscles of the eye-"polioencephalitis superior" (Pfluger, Guttmann, Goldflamm, Uhthoff, Schirmer). Further: Unilateral paralysis of the hypoglossal, with or without hemiatrophy of the tongue (Leyden, Flatten); paralysis of one recurrent laryngeal nerve (Trakauer); nuclear bulbar paralysis (Remak, Stembo, Guement, Fiessinger, Swiss report). Finally, isolated paralysis of one facial nerve without otitis (Laache); complete paralysis of one arm (Henoch, Bernhardt); atrophic paralysis in the distribution of certain shoulder, pectoral, and upper arm nerves, of the deltoid, supraspinatus, and infraspinatus, trapezius, serratus pectoralis- "the scapulohumeral type" (Teissier, Joffroy).
We may include as belonging to neuritis isolated reports of single or combined paralyses of the radial, ulnar, and median nerves (Draper and German army report) and individual nerves of the lower extremity, the peroneal, tibial, and crural; also some monoplegias and paraplegias occurring during convalescence without any alarming symptoms of cerebrospinal disease (Henoch, Barhdt, Warfvinge, Riener), which may be most easily explained as the paralyses due to neuritis.
The paralyses due to neuritis and nuclear affections arise almost exclusively after influenza has run its course, frequently even a few weeks after, just like many similar postdiphtheric paralyses.