Jonathan Lethem, discussing Ian McEwan's work, argued in 2007 that “neurology” has replaced “psychoanalysis” as today's great “rival to the novel's authority.” This essay explores Lethem's proposition via attention to these discourses' differing notions of the symptom. While Freud states in Studies on Hysteria that “it is difficult to attribute too much sense” to what may seem minor details (such as tics), neurology tends to grant them no meaning whatsoever. Where does this leave a literary-critical hermeneutics that has tended to take the Freudian view here as its default model? In place of either of these poles, I extended Gilles Deleuze's notion of fiction as a form of “symptomatology” by focusing not on the revelation of the symptom's “latent content” or its lack thereof but instead on what Slavoj Žižek has described as its elaboration of that content as a consequence of investing it with a libidinal charge. Lethem's novel Motherless Brooklyn (1999) offers a case study in which the narrator Lionel's Tourettic tics gain significance not for some psycho-biographical cause they reveal but for their effects, on the reader as much as on the world of the text itself. In both cases, the tic or repeated, jarring detail reorganizes the realist space momentarily in the mode of perversity, reopening its narrative frame to discordant echoes from the literary past (satire) and future (modernism). The symptom is thus mobilized in its specificity to refuse the etiological model that psychoanalysis and neurology often share, which emphasizes a linear progression from cause to resolution.