The possibility of a close relationship between BPVC and migraine and the idea that BPVC may be considered as a “migraine variant” or “migraine precursor” or “migraine equivalent” were first suggested by Fenichel in 1967 in a report of “two siblings who displayed a syndrome of benign paroxysmal vertigo and in whom the attacks progressively converted into classical migraine”. Fenichel’s hypothesis was in contrast with that of Basser [1] who considered “benign paroxysmal vertigo of childhood a variety of vestibular neuronitis.” Basser’s opinion was mainly based on the observation that in BPVC children, “the caloric tests typically demonstrated moderate, severe or complete canal paresis”; however, this finding was not confirmed in the large majority of subsequent studies [30].

In the following years, Fenichel’s hypothesis (“the suggestion is therefore made that “benign paroxysmal vertigo of childhood” may at times be an early manifestation of migraine rather than a form of vestibular neuronitis”) was confirmed in a series of following publications in which the terms of “migraine equivalent” or “migraine precursor” were expressly used [8, 13, 24, 31, 32]; this idea is more or less accepted in all studies related to BPVC that have been published in the last three decades. In our opinion, the contributions of population-based studies [16, 24] and studies in which long-term follow-up has been possible are of particular significance [14, 17, 19].

Epidemiological, clinical, and genetic findings support the hypothesis of a relationship between BPVC and migraine.

First, a higher rate of familial history of migraine in children with BPVC than in normal population has been demonstrated, ranging between 53 and 100 %, while motion sickness in parents was reported in 83 % of cases [10, 18, 33]. In a population-based study on 2,165 children [24], the authors described a prevalence rate of BPVC of 2.6 % and of migraine of 8 %; BPVC patients also presented clinical features in common with children with a diagnosis of migraine, including triggering and relieving factors, associated gastrointestinal and sensory symptoms, motion sickness, and a similar pattern of associated recurrent disorders (such as headache, abdominal pain, and cyclical vomiting). Finally, these children presented a twofold increase in the prevalence of migraine (24 %) compared with the general childhood population (10.6 %), while the prevalence rate of BPVC in children with migraine was three times higher than in the general childhood population. In another study [10], the presence of migraine equivalents was assessed on a population of 108 children with periodic syndromes followed over a 8-year period; BPVC was reported in 38 % of cases, while CVS in 18.5 % and benign paroxysmal torticollis in 10.2 %. Other studies have focused on an association between BPVC and other forms of periodic syndromes (atopy and motion sickness above all); moreover, migraine and BPVC often present the same triggering and relieving factors [14, 17, 18]. Finally, headache provocation tests with nitroglycerin, histamine, and fenfluramine were demonstrated to be positive in 9 of 13 patients with BPVC and in 4 cases induced a typical vertiginous attack instead of headache [13].

Several investigations have reported that a high rate of BPVC children develop migraines as adults. In a follow-up of seven BPVC children, Lanzi et al. [14] reported that six developed migraine after the age of 20 years; in studies based on larger patient cohorts, the development of migraine after the age of 15 years was reported to occur in 21–100 % of BPVC patients [17, 19].

Genetic factors underlying common pathophysiological mechanisms between migraine and BPVC have been studied [34, 35]. In a small sample of four BPVC patients, two of who originated from a kindred with familial hemiplegic migraine linked to CACNA1A mutation [36]; in another study, a novel variant of CACNA1A mutation was found in a patient displaying a changing, age-specific phenotype that began as benign paroxysmal torticollis of infancy, evolving into benign paroxysmal vertigo of childhood, and later becoming hemiplegic migraine [37].

These considerations led the International Headache Society (IHS) to include BPVC, together with cyclical vomiting and abdominal migraine, in the first International Classification of Headache Disorders under the chapter “Migraine (1)” and the subtype “Childhood periodic syndromes that are commonly precursor of migraine (1.3),” without modifications in the second edition [3, 4]. The third edition, now in progress (ICHD-3 beta version, 2013) [5], includes minor modifications in the denomination and classification of these disorders under the code “Migraine (1)”: “Episodic syndromes that may be associated with migraine (1.6),” “Recurrent gastrointestinal disturbance (1.6.1),” comprising “Cyclic vomiting syndrome (1.6.1.1)” and “Abdominal migraine (1.6.1.2),” “Benign paroxysmal vertigo (1.6.2),” “Benign paroxysmal torticollis (1.6.3).”

However, the official description and clinical features of BPVC (finally called simply benign paroxysmal vertigo) is unvaried: “This probably heterogeneous disorder is characterized by recurrent brief episodic attacks of vertigo occurring without warning and resolving spontaneously in otherwise healthy children.” In the Appendix of the ICHD-3, the possible relationship between BPV and the new entity “Vestibular migraine (A1.6.5)” is discussed.

Some authors have hypothesized two distinct forms of BPVC:

The first form has been defined as “classic BPVC” or “classic Basser” and considered as a migraine precursor; the second group was defined as “atypical” or “migrainous” paroxysmal vertigo and considered as a migraine equivalent [14, 17, 20, 21]. According to these authors, the first form of BPVC could be expression of a neurodevelopmental anomaly that resolves spontaneously, while the second form is linked to a functional chronic neurological disorder, although both may have the same genetic basis and similar pathophysiological mechanisms. However, this difference is based on a limited number of cases and the distinction between the two forms, in our opinion, is as yet unjustified; in our experience, the terms “precursor,” “equivalent,” or “variant” may be considered to be mostly synonyms.

The theory that BPVC is a form of childhood migraine is a compelling one. Migraine is a complex polygenic disorder [38] with clinical heterogeneity, and in different individuals or in different ages in the same individual life span, it may occur with different clinical manifestations, depending on its targets within the nervous system: classic migraine headache in case of involvement of the trigemino-vascular system (typical migraine or, preferred, migrainous headache or trigemino-vascular migraine, with or without aura); paresthesias, ataxia, and visual disorders when the brainstem and cerebellar system is involved (basilar-type migraine); vertigo and/or dizziness in case of involvement of the vestibular system (vestibular migraine); scotomata and/or blindness in case of involvement of the visual system (retinal migraine); and vomiting and/or motion sickness in case of involvement of the neurovegetative system (cyclic vomiting).

Benign paroxysmal torticollis (BTP) is a rare clinical disorder characterized by recurrent episodes of cervical dystonia. It was first described by Snyder [39] in 1969, who reported 12 cases, and in 11, the onset was in infancy; since in nine of 12 subjects the author found abnormal caloric tests, he considered this disorder as a possible clinical manifestation of labyrinthitis in infancy. To date, around 100 cases have been described in the medical literature, although in some the final diagnosis is missing. Among various causes of torticollis, benign paroxysmal torticollis is far from being frequent: in a study on a large sample (700 cases of primary torticollis in developmental age), only 7 had a final diagnosis of benign torticollis of infancy [40]. A female preponderance has been reported, ranging between 58 and 70 % of cases [23, 41]. According to previous reports, the age of onset of clinical symptoms ranges from 1 week to 30 months, with a mean of 5.9 months; in 75 % of cases, the first episode begins within the 7th month of life, and in 95 %, within the first 14 months.