Neurocysticercosis: the good, the bad, and the missing

Figures & data

Table 1. Differences between parenchymal and extraparenchymal neurocysticercosis.

	Parenchymal	Extraparenchymal
		Subarachnoideal		Intraventricular
		Cysts in basal cisterns	Arachnoiditis
Main clinical manifestations	Seizures, focal deficits	Cranial hypertension	Cranial hypertension, symptoms of cranial neuropathy	Cranial hypertension, Bruns’ syndrome
Pathology	Focal tissue inflammation and/or gliosis	Mass effect	Thickening of leptomeninges	Obstruction of CFS circulation
CSF analysis	Often inconclusive	Inflammatory pattern	Inflammatory pattern	Inflammatory pattern (less intense than in subaracnoidal parasites)
Immunological tests	Antibodies >50%, antigens <50%	–	Antibodies >90%, antigens >70%	Antibodies >90%, antigens >70%
Complications	Epilepsy, cognitive decline	Hydrocephalus, vasculitis, cerebral infarcts, chiasmatic syndrome	Hydrocephalus, vasculitis, cerebral infarcts, chiasmatic syndrome	Hydrocephalus, ependymitis, sudden death
Prognosis	Good, clinical manifestations usually self-limited	‘Malignant,’ clinical manifestations usually progressive	‘Malignant,’ usually permanent sequelae	Heterogeneous. Can be good after excision by endoscopic surgery

Figure 1. Imaging of parenchymal and extraparenchymal neurocysticercosis.

(A) MRI post-gadolinium T1 sequence showing viable cysts with scolex (thin arrows) and a transitional or degenerative-choloidal cyst (wide arrow).(B) CT scan showing multiple parenchymal calcifications (arrows).(C) 3D MRI sequence (FIESTA) showing cysts into the left ventricle (arrow).(D) 3D MRI sequence (FIESTA) showing cysticerci at the right cerebellopontine cistern (arrow).

Figure 2. Multifactorial basis of epilepsy in patients with neurocysticercosis. (A) Three factors involved in epileptogenesis in NC. (Top) Sinuous line indicates seizure threshold or propensity for a seizure to occur. (Middle) Represents structural lesion due to the parasite evolutionary phase that changes over time: a, viable; b, colloidal; c, granular-nodular; and d, calcified cyst. The evolution of cysts phases lasts around 6 months on average, from the viable to calcified stage. (Bottom) Arrows illustrate potential precipitating factors or a cascade of mechanisms that may contribute to trigger seizures. Someone with a high threshold may have parasitic epileptogenic lesions and never have seizures (i.e. asymptomatic patients). (B) Someone with a low threshold could have acute seizures, as indicated by the red lines around the cysts (i.e. ictogenesis) due to parasitic epileptogenic lesions and precipitating factors, and seizures recur over time since there is a genetic predisposition to maintain low threshold (i.e. epileptogenesis). (C) Someone with a low threshold could have acute seizures due to parasitic epileptogenic lesions and precipitating factors, but seizures do not recur, since there is no genetic predisposition to maintain a low threshold and they do not evolve into epilepsy. Republished with permission from [51].

Table 2. New diagnostic criteria for symptomatic neurocysticercosis.

1. Parenchymal neurocysticercosis
	Definitive parenchymal neurocysticercosis^a, one of the following:
		(1) Parenchymal cyst with pathological diagnosis
		(2) Single or multiple active parenchymal cysts, with at least one cyst with scolex on CT or MRI
		(3) Multiple parenchymal vesicles without scolex associated with at least one of the following:
			(a) Seizures: focal or generalized tonic-clonic
			(b) Positive serum or CSF immunological test (ELISA, EITB)
		(4) Any combination of the parenchymal cysticercus in different evolutive stages: vesicular with or without scolex, degenerative (colloidal or nodular) and calcified
	Probable parenchymal neurocysticercosis, one of the following:
		(1) Single parenchymal calcification or vesicle (without scolex) or degenerating cyst(s), establishing differential diagnoses with other etiologies, associated with at least two of the following:
			(a) Seizures: focal or generalized tonic-clonic
			(b) Subcutaneous or muscle cysts location confirmed by biopsy
			(c) Positive serum or CSF immunological test (ELISA, EITB)
			(d) Plain X-ray films showing ‘cigar-shaped’ calcifications
			(e) Individual who lives or has lived in or has traveled frequently to endemic countries
		(2) Multiple parenchymal calcifications in an individual who lives or has lived in or has traveled frequently to endemic countries and in whom clinical state excludes other etiologies of calcifications
2. Extraparenchymal neurocysticercosis (intraventricular/basal subarachnoid)
	Definitive extraparenchymal neurocysticercosis, one of the following:
		(1) Extraparenchymal cyst with pathological diagnosis
		(2) One or more extraparenchymal cysts on MRI special sequences with scolex in at least one of them
		(3) One or more extraparenchymal cysts on MRI special sequences without scolex associated with at least two of the following:
			(a) Hydrocephalus
			(b) Inflammatory CSF
			(c) Positive CSF immunological test (ELISA, EITB)
			(d) Presence of single or multiple calcifications or parenchymal vesicular or degenerative cyst
3. Definitive parenchymal and extraparenchymal neurocysticercosis
		Combination of the above definitive parenchymal and definitive extraparenchymal criteria

^aParasite located in the subarachnoid space of the convexity is included with parenchymal parasites.

From Ref. [36]

CT: computed tomography; MRI: magnetic resonance imaging; CSF: cerebrospinal fluid; ELISA: enzyme-linked immunosorbent assay; EITB: enzyme-linked immunoelectrotransfer blot.

Table 3. Treatment of neurocysticercosis.

	Parenchymal^f	Subarachnoideal		Intraventricular
		Cysts in basal cisterns	Arachnoiditis
Symptomatic therapy	Antiseizures, analgesics, and steroids drugs according to clinical manifestations^a	Ventriculo peritoneal shunt for clinical intracranial hypertension management and steroids^a	Analgesics and steroids drugs according to clinical manifestations^a; ventriculo peritoneal shunt for hydrocephalus^a	Ventriculo peritoneal shunt for hydrocephalus^a and steroids^a
Antihelminthic drugs	Albendazole or praziquantel^d for vesicular cysts^b or single enhancing cyst^c	Albendazole or praziquantel^a,e	No indication^a	Albendazole or praziquantel ^a,e
Surgical treatment	Excision of ‘giant’ cyst with mass effect^a	No indication^a	No indication^a	Neuroendoscopic excision^a

^aThere is no controlled clinical trial; ^bbased on controlled clinical trials (30–40% of disappearance of cysts); ^ccontroversial results of clinical trials; ^dalbendazole 15 mg/kg/day for 1 week, praziquantel 50 mg/kg/day for 2 weeks (usual doses recommended by consensus); ^edoses of albendazole or praziquantel have not been systematically standardized although 30 mg/kg of albendazole was reported more efficient than the classical doses of 15 mg/kg/day in one randomized study (Gongora-Rivera et al.); ^fincludes cysts in sulcus of the convexity.

Table 4. Controlled clinical trials regarding effects of albendazole on resolution of viable parenchymal cysts and seizures recurrence.

Author, year	Treatment groups (No. patients)	Patients with cysts disappearance^a No. patients (%)	Seizure recurrence^b No. patients (%)
Garcia et al., 2004	Albendazole (55)	21 (38)	32 (56)
	Placebo (54)	8 (15)	32 (54)
Das et al., 2007	Albendazole (148)	10 (7)	40 (27)
	Placebo (150)	12 (8)	24 (16)
Carpio et al., 2008	Albendazole (51)	18 (35)	19 (38)
	Placebo (50)	6 (12)	27 (48)
Kaur et al., 2009^c	Albendazole plus Praziquantel (53)	38 (72)	3 (0.5)
	Placebo(50)	26 (52)	3 (0.6)
Garcia et al., 2014	Albendazole plus Praziquantel (41)	64	NA
	Only albendazole (43)	37	NA

^aImaging at 6 months after finishing treatment. ^bSeizures recurrence at 1-year follow-up (except Das et al., study, with 6-month follow-up): All these results were not statistically significant. ^cPatients with single enhancing lesion.

NA: not available.

Carpio A, Romo ML. Multifactorial basis of epilepsy in patients with neurocysticercosis. Epilepsia. 2015;56:973–974.

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Carpio A, Fleury A, Romo ML, et al. New diagnostic criteria for neurocysticercosis: reliability and validity. Ann Neurol. 2016;80:434–442.

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