Nodding syndrome

Abstract

An epidemic illness characterized by head nodding associated with onchocerciasis has been described in eastern Africa since the early 1960s; we summarize published reports and recent studies. Onset of nodding occurs in previously healthy 5-15-year-old children and is often triggered by eating or cold temperatures and accompanied by cognitive impairment. Its incidence has increased in Uganda and South Sudan over the past 10 years. Four case-control studies identified modest and inconsistent associations. There were nonspecific lesions seen by magnetic resonance imaging, no cerebrospinal fluid inflammation, and markedly abnormal electroencephalography results. Nodding episodes are atonic seizures. Testing has failed to demonstrate associations with trypanosomiasis, cysticercosis, loiasis, lymphatic filariasis, cerebral malaria, measles, prion disease, or novel pathogens; or deficiencies of folate, cobalamin, pyridoxine, retinol, or zinc; or toxicity from mercury, copper, or homocysteine. There is a consistent enigmatic association with onchocerciasis detected by skin snip or serologic analysis. Nodding syndrome is an unexplained epidemic epilepsy.

Keywords: Africa; Nodding syndrome; South Sudan; Uganda; epidemic; epilepsy; head nodding; idiopathic; onchocerciasis; parasites; seizures.

Figure 1

Child with nodding syndrome, on whom electroencephalographic leads are being attached, Uganda, 2009.

Figure 2

Epidemic curve of nodding syndrome cases in Kitgum District, Uganda, by year of onset. Modified from Foltz et al. (6).

Figure 3

Countries in the former Onchocerciasis Control Programme in western Africa in which onchocerciasis was eliminated as a public health problem through vector control (green); countries in the African Programme for Onchocerciasis Control in which onchocerciasis control is ongoing through annual mass treatment with ivermectin (beige); and areas in Southern Sudan, northern Uganda, and southern Tanzania in which nodding syndrome has been reported (red circles).

Figure 4

Age distribution of patients at onset of nodding syndrome, Kitgum District, Uganda. For nodding syndrome elsewhere, age distribution tightly clusters in persons 5–15 years of age. Modified from Foltz et al. (6).

Figure 5

Ictal electroencephalographic recording of a 12-year-old boy in Uganda with nodding syndrome obtained during a typical nodding episode. Shown is a sudden electrodecremental episode with concomitant electromyographic decrease in neck muscles, followed by sharply contoured theta activity.

Figure 6

Magnetic resonance image of a 13-year-old boy in Uganda with nodding syndrome. Image shows prominent cortical atrophy.