Gelastic seizures in a child with focal cortical dysplasia of the cingulate gyrus

Anterior Cingulate Epilepsy: A Review

SUMMARY

In this review, the semiology, and characteristics of noninvasive investigations suggestive of anterior cingulate and anterior midcingulate epilepsy are detailed by the authors. The clinical presentation is representative of a recently recognized rostrocaudal gradient of functional connectivity with seizures of the anterior cingulate cortex manifesting emotional and interoceptive aura followed by a hyperkinetic or complex motor seizures. The few reports of anterior midcingulate epilepsy show a trend toward a higher proportion of sensory auras and premotor semiology. Ictal pouting, vocalizations, and, in particular, laughter are strong indicators of epilepsy arising or spreading to this region. Although scalp EEG was traditionally thought to provide little information, the data provided in this review demonstrate that most patients will have abnormalities over the frontal or frontotemporal regions. Frontotemporal abnormalities at least interictally provide valuable information regarding lateralization. The etiology of epilepsy arising from the anterior cingulate region seems to be most frequently secondary to focal cortical dysplasia (FCD), followed by neoplasms and vascular lesions, particularly cavernomas, although one cannot rule out a publication bias. Findings of nuclear medicine imaging is seldomly reported but both positron emission tomography and ictal single-photon computed tomography can identify the generator or the network often showing abnormalities extending to the frontal regions. The few available magnetoencephalography (MEG) studies reveal mixed results, sometimes providing false lateralization of the focus. Anterior cingulate epilepsy is difficult to recognize, but the features summarized in this review should prompt suspicion in clinical practice.

The Local Topological Reconfiguration in the Brain Network After Targeted Hub Dysfunction Attacks in Patients With Juvenile Myoclonic Epilepsy

The central brain regions of brain networks have been extensively studied in terms of their roles in various diseases. This study provides a direct measure of the brain's responses to targeted attacks on central regions, revealing the critical role these regions play in patients with juvenile myoclonic epilepsy (JME). The resting-state data of 37 patients with JME and 37 healthy subjects were collected, and brain functional networks were constructed for the two groups of data according to their Pearson correlation coefficients. The left middle cingulate gyrus was defined as the central brain region by the eigenvector centrality algorithm and was attacked by the CLM sequential failure model. The rich-club connection differences between the patients with JME and healthy controls before and after the attacks were compared according to graph theory indices and the number of rich-club connections. We found that the numbers of rich connections in the brain networks of the healthy control group and the group of patients with JME were significantly reduced [p < 0.05, false discovery rate (FDR) correction] before the CLM sequential failure attacks, and no significant differences were observed between the feeder connections and local connections. In the healthy control group, significant rich connection differences were obtained (p < 0.01, FDR correction), and no statistically significant differences were observed regarding the feeder connections and local connections in the brain network before and after CLM failure attacks on the central brain region. No significant differences were obtained between the rich connections, feeder connections, and local connections in patients with JME before and after CLM successive failure attacks on the central brain area. The rich connections, feeder connections, and local connections were not significantly different in the brain networks of the healthy control group and the group of patients with JME after CLM successive failure attacks on the central brain region. We concluded that the damage to the left middle cingulate gyrus is closely linked to various brain disorders, suggesting that this region is of great importance for understanding the pathophysiological basis of myoclonic seizures in patients with JME.

The spectrum of involuntary vocalizations in humans: A video atlas

In clinical practice, involuntary vocalizing behaviors are typically associated with Tourette syndrome and other tic disorders. However, they may also be encountered throughout the entire tenor of neuropsychiatry, movement disorders, and neurodevelopmental syndromes. Importantly, involuntary vocalizing behaviors may often constitute a predominant clinical sign, and, therefore, their early recognition and appropriate classification are necessary to guide diagnosis and treatment. Clinical literature and video-documented cases on the topic are surprisingly scarce. Here, we pooled data from 5 expert centers of movement disorders, with instructive video material to cover the entire range of involuntary vocalizations in humans. Medical literature was also reviewed to document the range of possible etiologies associated with the different types of vocalizing behaviors and to explore treatment options. We propose a phenomenological classification of involuntary vocalizations within different categorical domains, including (1) tics and tic-like vocalizations, (2) vocalizations as part of stereotypies, (3) vocalizations as part of dystonia or chorea, (4) continuous vocalizing behaviors such as groaning or grunting, (5) pathological laughter and crying, (6) vocalizations resembling physiological reflexes, and (7) other vocalizations, for example, those associated with exaggerated startle responses, as part of epilepsy and sleep-related phenomena. We provide comprehensive lists of their associated etiologies, including neurodevelopmental, neurodegenerative, neuroimmunological, and structural causes and clinical clues. We then expand on the pathophysiology of the different vocalizing behaviors and comment on available treatment options. Finally, we present an algorithmic approach that covers the wide range of involuntary vocalizations in humans, with the ultimate goal of improving diagnostic accuracy and guiding appropriate treatment. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Cingulate seizures and recent treatment strategies

Cingulate epilepsy manifests with a broad range of semiologic features and seizure types. Key clinical features may elucidate ictal involvement of certain subregions of the cingulate gyrus. Ictal and interictal electroencephalogram findings in cingulate epilepsy vary and are often poorly localized, adding to the diagnostic challenge of identifying the seizure onset zone for presurgical cases, particularly in the absence of a lesion on imaging. Recent advances in multimodal imaging techniques may contribute to ictal localization and further our understanding of neural and epileptic pathways involving the cingulate gyrus. Beyond medication and surgical resection, new techniques including stereotactic laser ablation, responsive neurostimulation, and deep brain stimulation offer additional approaches for the treatment of cingulate epilepsy.

Spiders, ladybugs and bees: A case of unusual sensations in a child with cingulate epilepsy

Cingulate epilepsy is a rare form of epilepsy. Seizures from the anterior cingulate may present with mood change, fear, hypermotor activity, and autonomic signs, while posterior cingulate seizures resemble temporal lobe seizures. We describe a child with cingulate epilepsy who experienced unpleasant/painful sensory phenomenon. The sensations were described as spiders crawling on his forehead/right leg, ladybugs causing right ear pain and bees stinging his head/right extremities. Unpleasant sensory phenomenon/pain are rarely reported in cingulate epilepsy. Recognizing the role of the cingulate in producing pain/unusual sensory phenomenon is important, and may have localizing value when evaluating children for epilepsy surgery.

Smile without euphoria induced by deep brain stimulation: a case report

Poststroke central pain (PSCP) can be a debilitating medication-refractory disorder. We report a single case where right unilateral ventral capsule/ventral striatum (VC/VS) deep brain stimulation was used to treat PSCP and inadvertently induced a smile without euphoria. The patient was a 69 year-old woman who had a stroke with resultant dysesthesia and allodynia in her left hemibody and also a painful left hemibody dystonia. In her case, VC/VS stimulation induced a smile phenomenon, but without a euphoric sensation. This phenomenon was different from the typical smile responses we have observed in obsessive-compulsive disorder cases. This difference was considered to be possibly attributable to impairment in the emotional smile pathway.

Different localizations underlying cortical gelastic epilepsy: case series and review of literature

BACKGROUND

Gelastic seizures (GS) are classically observed with hypothalamic hamartomas but they can also be associated with cortical epileptogenic foci.

OBJECTIVE

To study the different cortical localizations associated with GS.

METHODS

We reviewed the data from all patients with cortical GS investigated in our epilepsy unit from 1974 to 2012 and in the literature from 1956 to 2013.

RESULTS

Sixteen cases were identified in our database and 77 in the literature. Investigations provided confident focus localization in 9 and 18, respectively. In our series, the identified foci were located in the mesial temporal structures (2 left, 1 right), lateral temporal cortex (1 right), superior frontal gyrus (1 left), and operculoinsular region [3 right (orbitofrontal or frontal operculum extending into the anterior insula) and 1 left (frontal operculum extending into the anterior insula)]. In the literature, the identified foci (13 right/5 left) were located in the temporal lobe of 4 (1 right inferior, 1 right medial and inferior, 1 right posterior middle, inferior extending posteriorly to the lingual gyrus, and 1 left middle, inferior, and medial), in the frontal lobe of 12 [10 (6 right/4 left) medial (i.e., superior, medial frontal, and/or anterior cingulate gyri), 1 lateral (right anterior inferior frontal gyrus), and 1 right medioposterior orbitofrontal cortex] and in the parietal lobe of 2 (1 left superior parietal lobule and 1 right parietal operculum) patients.

CONCLUSION

Ictal laughter is a poorly lateralizing and localizing feature as it may be encountered in patients with a focus in the left or right frontal, temporal, parietal, or insular lobe.

Cingulate epilepsy: report of 3 electroclinical subtypes with surgical outcomes

IMPORTANCE

The literature on cingulate gyrus epilepsy in the magnetic resonance imaging era is limited to case reports and small case series. To our knowledge, this is the largest study of surgically confirmed epilepsy arising from the anterior or posterior cingulate region.

OBJECTIVE

To characterize the clinical and electrophysiological findings of epilepsies arising from the anterior and posterior cingulate gyrus.

DESIGN, SETTING, AND PARTICIPANTS

We studied consecutive cingulate gyrus epilepsy cases identified retrospectively from the Cleveland Clinic and University of Texas Southwestern Medical Center epilepsy databases from 1992 to 2009. Participants included 14 consecutive cases of cingulate gyrus epilepsies confirmed by restricted magnetic resonance image lesions and seizure freedom or marked improvement following lesionectomy.

MAIN OUTCOMES AND MEASURES

The main outcome measure was improvement in seizure frequency following surgery. The clinical, video electroencephalography, neuroimaging, pathology, and surgical outcome data were reviewed.

RESULTS

All 14 patients had cingulate epilepsy confirmed by restricted magnetic resonance image lesions and seizure freedom or marked improvement following lesionectomy. They were divided into 3 groups based on anatomical location of the lesion and corresponding seizure semiology. In the posterior cingulate group, all 4 patients had electroclinical findings suggestive of temporal origin of the epilepsy. The anterior cingulate cases were divided into a typical (Bancaud) group (6 cases with hypermotor seizures and infrequent generalization with the presence of fear, laughter, or severe interictal personality changes) and an atypical group (4 cases presenting with simple motor seizures and a tendency for more frequent generalization and less-favorable long-term surgical outcome). All atypical cases were associated with an underlying infiltrative astrocytoma.

CONCLUSIONS AND RELEVANCE

Posterior cingulate gyrus epilepsy may present with electroclinical findings that are suggestive of temporal lobe epilepsy and can be considered as another example of pseudotemporal epilepsies. The electroclinical presentation and surgical outcome of lesional anterior cingulate epilepsy is possibly influenced by the underlying pathology. This study highlights the difficulty in localizing seizures arising from the cingulate gyrus in the absence of a magnetic resonance image lesion.

Gelastic seizures and fever originating from a parietal cortical dysplasia

Gelastic seizures (GS) is an uncommon seizure type characterized by sudden inappropriate attacks of uncontrolled and unmotivated laugh and its diagnostic criteria were elaborated by Gascon. These criteria included stereotypical recurrence of laugh, which is unjustified by the context, associated signs compatible with seizure, and ictal or interictal abnormalities. GS can be cryptogenic or symptomatic of a variety of cerebral lesions, the most common being hypothalamic hamartoma. However, GS associated with other types of cerebral lesions are exceedingly rare. The physiopathologic mechanisms of this type of seizure are still undefined. Two reports have described a non-lesional GS arising from a parietal focus. In this paper, we report the first case of lesional GS associated to the parietal area of the brain in a child and this case has associated fever that is likely an ictal symptom.

Whole-exome sequencing of a unique brain malformation with periventricular heterotopia, cingulate polymicrogyria and midbrain tectal hyperplasia

We report a case of an infant with unique and unreported combinations of brain anomalies. The patient showed distinctive facial findings, severe delay in psychomotor development, cranial nerve palsy and seizures. Brain magnetic resonance imaging performed at 5 days of age revealed complex brain malformations, including heterotopia around the mesial wall of lateral ventricles, dysmorphic cingulate gyrus, and enlarged midbrain tectum. The patient unexpectedly died at 13 months of age. Postmortem pathological findings included a polymicrogyric cingulate cortex, periventricular nodular heterotopia, basal ganglia and thalamic anomalies, and dysmorphic midbrain tectum. Potential candidate genes showed no abnormalities by traditional PCR-based sequencing. Whole-exome sequencing confirmed the presence of novel gene variants for filamin B (FLNB), guanylate binding protein family member 6, and chromosome X open reading frame 59, which adapt to the autosomal recessive mode or X-linked recessive mode. Although immunohistochemical analysis confirmed the expression of FLNB protein in the vessel walls and white matter in autopsied specimens, there may be functional relevance of the compound heterozygous FLNB variants during brain development.

Cingulate gyrus epilepsy: clinical and behavioral aspects, with surgical outcomes

BACKGROUND

Cingulate gyrus epilepsy is controversial because it may overlap with other frontal lobe epilepsy syndromes. Reported cases are rare in the pre-magnetic resonance imaging literature but are more common thereafter. Information about peri-ictal and ictal behaviors is scarce.

OBJECTIVES

To characterize epilepsy originating from the cingulate gyrus and to report surgical outcomes.

DESIGN

Case studies.

SETTING

Academic research.

PATIENTS

We report 3 surgically treated cases of cingulate gyrus epilepsy, with seizure-free or almost seizure-free outcomes. The cases were identified from a database of 4201 consecutive epilepsy monitoring unit admissions since October 1998 through September 2008. All 3 cases involved cingulate lesions.

MAIN OUTCOME MEASURES

Neuroimaging, video electroencephalographic, pathologic, and surgical outcome data were reviewed.

RESULTS

All 3 patients had lesional left anterocingulate seizures confirmed by magnetic resonance imaging and experienced cessation of seizures after lesionectomy. Two patients had auras (fear and laughter) previously associated with cingulate gyrus epilepsy. All patients had clinical features consistent with frontal lobe epilepsy, including hyperkinetic behavior and ictal vocalization. Two patients had behavioral changes with aggression, personality disorder, and poor judgment; some behavioral episodes lasted for days and were socially devastating. One patient, a commercial pilot, showed behavior as a passenger that resulted in a diversionary landing. The other patient demonstrated behavior that led to his arrest, and he was almost arrested again in the hospital for threatening security officers. Aberrant behaviors in all 3 patients completely resolved after lesionectomy.

CONCLUSIONS

Lesional cingulate gyrus epilepsy is uncommon. Our 3 confirmed cases included 2 patients with unique and severe behavioral changes that resolved with lesionectomy.

Gelastic seizures in tuberous sclerosis complex: case report and literature review

Gelastic seizures are typically associated with hypothalamic hamartoma. Given the rarity of gelastic seizures, pathways for the motor and emotional aspects of laughter have been hypothesized but remain unclear. The authors perform a literature review to discuss what is known about these pathways. They also report a child who presented with tuberous sclerosis complex initially without cutaneous stigmata, who later developed gelastic seizures. Only 2 case reports of patients with tuberous sclerosis complex who subsequently developed gelastic epilepsy have previously been reported. In discussing his case, the authors postulate additional etiologies for gelastic seizures.

Gelastic epilepsy and dysprosodia in a case of late-onset right frontal seizures

Gelastic epilepsy (GE) is an uncommon type of seizure disorder characterized by stereotyped, unprovoked, inappropriate ictal laughter. GE is most frequently associated with hypothalamic hamartoma, with onset almost invariably occurring during childhood. GE also occurs occasionally with temporal and frontal cortical seizure foci. We describe an unusual case of senescent-onset GE with a right frontal seizure focus. In addition to laughter, dysprosodia was a clinical feature. Clinical and electroencephalographic evidence of seizure activity ceased on levetiracetam, and the patient showed concurrent improvement in cognitive function. We review the evidence for the cerebral representation of laughter and prosody, and discuss issues bearing on the differential diagnosis and management of GE.

Analysis of dynamics and propagation of parietal cingulate seizures with secondary mesial temporal involvement

Cingulate-onset seizures, particularly those originating from parietal cingulate regions, are inadequately described and confounded by patterns of propagation. We analyzed scalp and depth electrode recordings in a patient whose seizures originated from a lesion in the right posterior cingulate region and produced secondary seizure activity in ipsilateral mesial temporal structures. Analyses included the matching pursuit (MP) method of time-frequency decomposition and the Gabor atom density (GAD) measure of signal complexity. Although scalp recordings suggested a right temporal onset, seizures recorded with depth electrodes clearly began in the parietal cingulate region before producing a secondary discharge in ipsilateral mesial structures. GAD revealed a significant increase in complexity during ictal cingulate activity and a consistent pattern of subsequent complexity changes in the hippocampus 30 seconds later. MP and GAD measures were valuable supplements to confirm the stereotyped pattern of both time-frequency changes and complexity. This provides additional evidence for pathways between the parietal cingulate region and mesial temporal structures and raises questions as to whether parietal cingulate seizures can produce clinical symptoms independent of regional or remote propagation.

Gelastic seizures associated with hypothalamic hamartomas. An update in the clinical presentation, diagnosis and treatment

Gelastic seizures are epileptic events characterized by bouts of laughter. Laughter-like vocalization is usually combined with facial contraction in the form of a smile. Autonomic features such as flushing, tachycardia, and altered respiration are widely recognized. Conscious state may not be impaired, although this is often difficult to asses particularly in young children. Gelastic seizures have been associated classically to hypothalamic hamartomas, although different extrahypothalamic localizations have been described. Hypothalamic hamartomas are rare congenital lesions presenting with the classic triad of gelastic epilepsy, precocious puberty and developmental delay. The clinical course of patients with gelastic seizures associated with hypothalamic hamartomas is progressive, commencing with gelastic seizures in infancy, deteriorating into more complex seizure disorder resulting in intractable epilepsy. Electrophysiological, radiological, and pathophysiological studies have confirmed the intrinsic epileptogenicity of the hypothalamic hamartoma. Currently the most effective surgical approach is the trancallosal anterior interforniceal approach, however newer approaches including the endoscopic and other treatment such as radiosurgery and gamma knife have been used with success. This review focuses on the syndrome of gelastic seizures associated with hypothalamic hamartomas, but it also reviews other concepts such as status gelasticus and some aspects of gelastic seizures in other locations.

Magnetoencephalography and diffusion tensor imaging in gelastic seizures secondary to a cingulate gyrus lesion

Gelastic seizures are relatively uncommon and rarely observed secondary to frontal lobe lesions. This report presents magnetoencephalography (MEG) and diffusion tensor imaging (DTI) findings in an adolescent with gelastic seizures secondary to a left anterior cingulate gyrus lesion. Ictal scalp video EEG showed bilateral frontal 4 Hz theta discharges. Interictal EEG showed left fronto-temporal spikes or sharp waves. Interictal MEG showed spike sources over bilateral temporal regions. DTI and tractography delineated slightly shifted corpus callosum posterior to the lesion, unaffected uncinate and inferior longitudinal fasciculi. The patient became seizure free for 12 months after surgical excision of a pleomorphic xanthoastrocytoma in the left anterior cingulate region. In our patient, MEG and EEG did not localize the deep-seated epileptogenic zone. The combination of DTI and neurophysiologic studies, however, possibly disclosed neuronal connections within the epileptic network and indicated that epileptic discharges propagated via the uncinate fibers from the primary epileptogenic zone in the anterior cingulate region to the mesial temporal region in this case with gelastic seizures secondary to a cingulate lesion.

Postictal laughter following absence status epilepticus

Acute pathologic neurologic laughter has been described as an ictal phenomenon in epilepsy, as a result of electrical brain stimulation to the cortex and to deep brain structures, in brain tumors, and in stroke. We report what is, to our knowledge, the first report of a case of postictal pathologic laughter. Previously diagnosed with medically refractory complex partial seizures, our patient was admitted to the hospital with phenytoin toxicity. During video-EEG monitoring she experienced multiple brief absence seizures as well as a prolonged episode of absence status epilepticus. Immediately following cessation of the seizure she began to laugh. Her laughter was mirthful and infectious. This lasted several minutes and was followed immediately by several minutes of crying and then a return to normal. We propose that diffuse cortical inhibition led to release of subcortical structures involved in emotional expression. Possible neural substrates of laughter are discussed.

Cortical innervation of the facial nucleus in the non-human primate: a new interpretation of the effects of stroke and related subtotal brain trauma on the muscles of facial expression

The corticobulbar projection to musculotopically defined subsectors of the facial nucleus was studied from the face representation of the primary (M1), supplementary (M2), rostral cingulate (M3), caudal cingulate (M4) and ventral lateral pre- (LPMCv) motor cortices in the rhesus monkey. We also investigated the corticofacial projection from the face/arm transitional region of the dorsal lateral premotor cortex (LPMCd). The corticobulbar projection was defined by injecting anterograde tracers into the face representation of each motor cortex. In the same animals, the musculotopic organization of the facial nucleus was defined by injecting fluorescent retrograde tracers into individual muscles of the upper and lower face. The facial nucleus received input from all face representations. M1 and LPMCv gave rise to the heaviest projection with progressively diminished intensity occurring in the M2, M3, M4 and LPMCd projections, respectively. Injections in all cortical face representations labelled terminals in all nuclear subdivisions (dorsal, intermediate, medial and lateral). However, significant differences occurred in the proportion of labelled boutons found within each functionally characterized subdivision. M1, LPMCv, LPMCd and M4 projected primarily to the contralateral lateral subnucleus, which innervated the perioral musculature. M2 projected bilaterally to the medial subnucleus, which supplied the auricular musculature. M3 projected bilaterally to the dorsal and intermediate subnuclei, which innervated the frontalis and orbicularis oculi muscles, respectively. Our results indicate that the various cortical face representations may mediate different elements of facial expression. Corticofacial afferents from M1, M4, LPMCv and LPMCd innervate primarily the contralateral lower facial muscles. Bilateral innervation of the upper face is supplied by M2 and M3. The widespread origin of these projections indicates selective vulnerability of corticofacial control following subtotal brain injury. The finding that all face representations innervate all nuclear subdivisions, to some degree, suggests that each motor area may participate in motor recovery in the event that one or more of these motor areas are spared following subtotal brain injury. Finally, the fact that a component of the corticofacial projection innervating both upper and lower facial musculature arises from the limbic proisocortices (M3 and M4) and frontal isocortices (M1, M2, LPMCv and LPMCd) suggests a potential anatomical substrate that may contribute to the clinical dissociation of emotional and volitional facial movement.

Gelastic seizures of neocortical origin confirmed by resective surgery

Ictal laughter is a relatively unusual phenomenon that appears to arise from within hypothalamic hamartomas. Gelastic seizures of neocortical origin are rare and when reported typically originate from temporofrontal regions in proximity to the hypothalamus, raising the possibility of a subtle lesion in the hypothalamus. A girl with gelastic seizures originating in a dysembryoblastic neuroepithelial tumor at the cranial vertex had resolution of her seizures following surgical resection. Electrical propagation of seizures via the cingulate gyrus appears to be an alternative mechanism underlying gelastic seizures.

Utility of early single photon emission computed tomography (SPECT) in neonatal gelastic epilepsy associated with hypothalamic hamartoma

Gelastic epilepsy, or laughing seizures, is a rare seizure manifestation often associated with hypothalamic hamartoma. This seizure type is well described in older children and adults, but has only rarely been reported in neonates, oftentimes recognized in retrospect when the children are older. We report a child diagnosed at 3 months of age with a large hypothalamic mass after evaluation for spells occurring since birth. The spells were characterized by bursts of hyperpnea, followed by repeated "cooing" respirations, giggling, and smiling. These spells were recognized soon after birth in the delivery room, and occurred at 15-20 minute intervals. They did not interrupt feeding and occurred during sleep. On referral to our center, the patient was noted to be thriving, with normal medical and neurologic examinations except for his spells. The laboratory evaluation was normal, as were endocrine and ophthalmologic evaluations. Neuroimaging was performed, with magnetic resonance imaging demonstrating a large 2.8-cm isodense, nonenhancing hypothalamic mass. Electroencephalogram was abnormal, demonstrating bi-frontal sharp and spike-wave discharges. Video-EEG did not demonstrate ictal discharges associated with the patient's spells. Single photon emission computed tomography (SPECT) demonstrated dramatic ictal uptake in the area of the tumor, with normalization during the interictal phase. Partial excision of hamartomatous tissue has minimally improved the spells. In conclusion, this patient manifested an unusual, early presentation of a rare seizure type. SPECT scanning confirmed the intrinsic epileptogenesis of the hamartoma, further justifying a surgical approach to such patients. Early surgical intervention is probably indicated in an attempt to minimize or prevent the cognitive and behavioral sequelae commonly seen with this seizure type.

Involuntary laughter and inappropriate hilarity

Laughter is a particularly human behavior. Neuropsychiatrists are faced with disorders of laughter, yet the nature of this behavior and its disturbances remains obscure. The authors report an unusual patient with involuntary and unremitting laughter for 20 years and review the literature. The nature of laughter suggests that it has a unique role in human communication, particularly in the social exploration of incongruous information. The disorders of laughter suggest a neuroanatomical circuitry that includes the anterior cingulate gyrus, caudal hypothalamus, temporal-amygdala structures, and a pontomedullary center. Treatment includes the use of antidepressant and antimanic agents for disorders of laughter.