Cluster headache

A 35-year-old man presents to the neurology clinic with severe episodic strictly unilateral orbital and periorbital pain. The current bout began 48 hours ago. The pain is excruciating and stabbing, reaches peak intensity rapidly, and lasts 30 to 90 minutes per episode. He reports associated ipsilateral eye redness, lacrimation, nasal congestion and/or rhinorrhea, ptosis, and miosis during attacks. The episodes occur multiple times daily, often at approximately the same time each day, especially at night, waking him from sleep. During attacks, he becomes restless and agitated and paces around the room. He has experienced similar headaches in the past, occurring in cycles lasting weeks to months, followed by pain-free remissions lasting at least 3 months to several years. Brain MRI, including the craniocervical junction, is normal. Diagnosis?

The diagnosis is cluster headache, most consistent with episodic cluster headache given the prolonged remission periods.

1. Definition

Cluster headache is a primary headache disorder classified among the trigeminal autonomic cephalalgias. It is characterized by attacks of severe or very severe strictly unilateral orbital, supraorbital, and/or temporal pain associated with ipsilateral cranial autonomic symptoms and/or restlessness or agitation.

Episodic cluster headache is characterized by at least two cluster periods lasting 7 days to 1 year when untreated, separated by pain-free remission periods lasting at least 3 months.

2. Etiology and Associations

1.      The exact etiology of cluster headache remains incompletely understood.

2.      A genetic contribution is supported by familial aggregation and genetic association studies.

3.      Smoking is strongly associated with cluster headache, and genetic epidemiological evidence suggests that smoking intensity may contribute causally to disease risk.

4.      Cluster headache has historically been reported more frequently in men, although it occurs in both sexes and the magnitude of the sex difference appears smaller than previously reported.

5.      Alcohol is an important trigger of individual attacks during an active cluster period, but it is not considered an established etiologic cause of cluster headache.

3. Pathophysiology

The pathophysiology of cluster headache remains incompletely understood and appears to involve interaction among the trigeminovascular system, trigeminal-autonomic reflex, hypothalamic networks, and circadian regulatory mechanisms.

3.1 Trigeminovascular System Activation

1.      Activation of trigeminal nociceptive pathways contributes to the severe unilateral head pain.

2.      Trigeminal activation is associated with release of neuropeptides, particularly calcitonin gene-related peptide (CGRP).

3.      Both peripheral and central nociceptive mechanisms are believed to contribute to pain generation and maintenance.

3.2 Trigeminal-Autonomic Reflex Activation

1.      Activation of trigeminal pathways stimulates cranial parasympathetic pathways involving the:

o    Superior salivatory nucleus

o    Facial nerve

o    Sphenopalatine ganglion

2.      Parasympathetic activation contributes to ipsilateral:

o    Lacrimation

o    Conjunctival injection

o    Nasal congestion

o    Rhinorrhea

o    Eyelid edema

3.3 Sympathetic Dysfunction

Ipsilateral miosis and ptosis represent a partial Horner-like sympathetic deficit that may occur during attacks.

3.4 Hypothalamic Involvement and Circadian Dysregulation

Hypothalamic and circadian network involvement is believed to contribute to:

1.      Circadian periodicity

2.      Nocturnal attacks

3.      Predictable timing of attacks

4.      Recurrent cluster periods

5.      Seasonal or circannual patterns in some patients

4. Clinical Features

1.      Severe or very severe strictly unilateral orbital, supraorbital, and/or temporal pain

2.      Pain may be described as:

o    Sharp

o    Stabbing

o    Piercing

Pain quality itself is not part of the formal ICHD-3 diagnostic criteria.

3.      Duration of an untreated attack:

o    15 to 180 minutes

4.      Attack frequency:

o    1 attack every other day to 8 attacks per day

5.      Attacks frequently:

o    Occur at approximately the same time each day

o    Occur during the night

o    Wake the patient from sleep

o    Occur in recurrent cluster periods lasting weeks to months

6.      In episodic cluster headache, cluster periods are separated by remission periods lasting at least 3 months.

4.1 Associated Features

Ipsilateral cranial autonomic symptoms and signs include:

1.      Conjunctival injection

2.      Lacrimation

3.      Nasal congestion

4.      Rhinorrhea

5.      Eyelid edema

6.      Forehead and facial sweating

7.      Miosis

8.      Ptosis

4.2 Behavioral Features

1.      Restlessness or agitation is highly characteristic.

2.      Patients may pace or move continuously during severe attacks.

3.      This contrasts with the typical behavior during migraine, in which patients often prefer to remain still, although this distinction is not absolute.

4.3 Other Characteristic Features

1.      Nocturnal attacks

2.      Circadian periodicity

3.      Recurrent cluster periods

4.      Prolonged pain-free remissions in episodic cluster headache

5.      Alcohol may precipitate an attack during an active cluster period

5. Diagnosis

The diagnosis is primarily clinical and is based on the International Classification of Headache Disorders, 3rd edition (ICHD-3) criteria.

5.1 ICHD-3 Diagnostic Criteria for Cluster Headache

The diagnosis requires:

1.      At least 5 attacks

2.      Severe or very severe strictly unilateral orbital, supraorbital, and/or temporal pain

3.      Untreated attack duration of 15 to 180 minutes

4.      At least one of the following:

o    One or more ipsilateral cranial autonomic symptoms or signs

o    A sense of restlessness or agitation

5.      Attack frequency ranging from 1 every other day to 8 per day

6.      The disorder is not better accounted for by another ICHD-3 diagnosis

5.2 Episodic Cluster Headache

Episodic cluster headache requires:

1.      At least two cluster periods

2.      Each cluster period lasts 7 days to 1 year when untreated

3.      Cluster periods are separated by pain-free remission periods lasting at least 3 months

The recurrent cluster periods and prolonged pain-free remissions described in this patient support the diagnosis of episodic cluster headache.

5.3 Neuroimaging

1.      For the initial diagnosis, brain MRI including the craniocervical junction is recommended to exclude secondary causes of cluster-like headache.

2.      Additional vascular or targeted imaging should be considered when:

o    Clinical features are atypical

o    Abnormal neurological findings are present

o    Red flags suggest a secondary headache disorder

o    A vascular, pituitary, inflammatory, or other structural disorder is suspected

3.      Routine dedicated pituitary MRI is not necessary unless symptoms, examination findings, or standard imaging raise suspicion for pituitary pathology.

4.      A normal MRI does not establish the diagnosis, because cluster headache remains a clinical diagnosis.

6. Management

Management consists of rapid termination of individual attacks, transitional therapy when appropriate, and preventive treatment during the active cluster period.

6.1 Acute Treatment

1. 100% Oxygen

·         Delivered through a non-rebreather mask

·         Flow rate of at least 12 L/min

·         Administered for approximately 15 minutes

2. Subcutaneous Sumatriptan

·         6 mg subcutaneously

·         One of the most effective pharmacological treatments for terminating an acute cluster headache attack

3. Alternative Acute Treatments

·         Intranasal sumatriptan 20 mg

·         Intranasal zolmitriptan 5 mg

Intranasal triptans generally have a slower onset of action than subcutaneous sumatriptan.

6.2 Preventive Treatment

Verapamil is the preventive treatment of choice.

·         Verapamil is recommended at a total daily dose of at least 240 mg, with gradual dose titration according to clinical response and tolerability.

·         A baseline ECG should be obtained before treatment.

·         Repeat ECG monitoring is required during dose escalation.

·         Continued ECG monitoring should be considered during higher-dose or prolonged therapy because clinically important conduction abnormalities may occur.

·         Blood pressure should also be monitored.

·         Potential cardiac adverse effects include:

o    Bradycardia

o    PR interval prolongation

o    Atrioventricular block

6.3 Transitional or Bridge Therapy

Transitional treatment may suppress attacks while a longer-term preventive treatment, particularly verapamil, becomes effective.

Options include:

1.      Corticosteroids

2.      Greater occipital nerve block

6.4 Alternative Preventive Treatments

Alternative preventive options include:

1.      Lithium

2.      Topiramate

Galcanezumab

·         Galcanezumab may be considered for prevention of episodic cluster headache.

·         Evidence supports efficacy in episodic cluster headache but has not demonstrated comparable efficacy in chronic cluster headache.

·         Regulatory approval and availability vary by country.

Melatonin

·         Melatonin may be considered as a later-line option, particularly when established preventive treatments are ineffective, contraindicated, or poorly tolerated.

·         Evidence supporting melatonin is limited compared with established preventive therapies.

7. Key Clinical Insight

Severe or very severe strictly unilateral orbital, supraorbital, and/or temporal pain lasting 15 to 180 minutes, accompanied by ipsilateral cranial autonomic symptoms and marked restlessness or agitation, particularly when attacks demonstrate circadian periodicity and occur in recurrent cluster periods, strongly suggests cluster headache.

In this patient, recurrent cluster periods separated by pain-free remissions lasting at least 3 months specifically support episodic cluster headache.

References

1.      Headache Classification Committee of the International Headache Society (IHS). The International Classification of Headache Disorders, 3rd edition. Cephalalgia. 2018;38(1):1-211. doi:10.1177/0333102417738202.

2.      May A, Evers S, Goadsby PJ, Leone M, Manzoni GC, Pascual J, et al. European Academy of Neurology guidelines on the treatment of cluster headache. European Journal of Neurology. 2023;30(10):2955-2979. doi:10.1111/ene.15956.

3.      Petersen AS, Lund N, Goadsby PJ, Belin AC, Wang SJ, Fronczek R, Burish M, Cho SJ, Peres MFP, Jensen RH. Recent advances in diagnosing, managing, and understanding the pathophysiology of cluster headache. The Lancet Neurology. 2024;23(7):712-724. doi:10.1016/S1474-4422(24)00143-1.

Gilbert Syndrome

A 20-year-old man presents with yellowing of the eyes for the past few days. He has no significant past medical history and reports recent examination-related stress. Vital signs are stable. Physical examination reveals mild scleral icterus. Laboratory investigations show a normal complete blood count, reticulocyte count, lactate dehydrogenase, and haptoglobin; normal AST, ALT, and ALP; total bilirubin of 2.4 mg/dL; and direct bilirubin of 0.2 mg/dL. There is no clinical or laboratory evidence of hemolysis. Diagnosis?

The diagnosis is Gilbert syndrome.

The total bilirubin is 2.4 mg/dL with a direct bilirubin of 0.2 mg/dL, indicating predominantly unconjugated hyperbilirubinemia. The direct fraction represents approximately 8% of the total bilirubin. The combination of isolated mild unconjugated hyperbilirubinemia, normal liver enzymes, absence of hemolysis, young age, and a typical precipitating factor strongly supports Gilbert syndrome.

1. Definition

Gilbert syndrome is a benign inherited disorder of bilirubin conjugation characterized by intermittent mild unconjugated hyperbilirubinemia in the absence of hemolysis or clinically significant liver disease.

It results from reduced expression or activity of uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1), the hepatic enzyme responsible for bilirubin glucuronidation.

2. Etiology and Genetics

1.      Gilbert syndrome results from genetic variants that reduce UGT1A1 expression or activity.

2.      The UGT1A1*28 promoter variant is a common cause in populations of European and African ancestry.

3.      Other variants, including coding-region variants such as UGT1A1*6, are particularly important in some Asian populations.

4.      The inheritance pattern is variant-dependent.

o    Gilbert syndrome associated with homozygous UGT1A1*28 generally follows an autosomal recessive pattern.

o    Some UGT1A1 missense variants associated with Gilbert syndrome can demonstrate autosomal dominant inheritance.

o    Clinical expression is variable because genotype alone does not completely determine serum bilirubin concentration.

3. Pathophysiology

1.      Heme derived primarily from senescent erythrocytes is metabolized to bilirubin.

2.      Unconjugated bilirubin circulates bound to albumin and is transported to the liver.

3.      Within hepatocytes, UGT1A1 conjugates bilirubin with glucuronic acid, making it more water-soluble and facilitating biliary excretion.

4.      In the classic form of Gilbert syndrome, UGT1A1 activity is reduced to approximately 30% of normal.

5.      Reduced bilirubin glucuronidation leads to accumulation of unconjugated bilirubin in the circulation.

6.      Serum bilirubin fluctuates over time and may increase during physiologic stress.

7.      Gilbert syndrome does not itself cause progressive hepatocellular injury, fibrosis, cirrhosis, or liver failure.

4. Clinical Features

4.1 Core Features

1.      Intermittent mild jaundice, often first noticed as scleral icterus

2.      Predominantly unconjugated hyperbilirubinemia

3.      Usually otherwise asymptomatic

4.      Frequently recognized during adolescence or young adulthood

5.      Normal liver examination in uncomplicated disease

6.      No hepatosplenomegaly attributable to Gilbert syndrome

7.      No clinical evidence of chronic liver disease

The jaundice may become apparent only when serum bilirubin rises transiently during physiologic or emotional stress.

4.2 Precipitating Factors

Serum bilirubin may increase during:

1.      Fasting or caloric restriction

2.      Intercurrent illness or fever

3.      Dehydration

4.      Physical exertion

5.      Physiologic or emotional stress

6.      Menstruation

Bilirubin concentrations typically fall toward baseline after the precipitating factor resolves.

5. Diagnosis

Gilbert syndrome is a clinical diagnosis supported by characteristic laboratory findings after hemolysis and clinically significant liver disease have been excluded.

5.1 Typical Laboratory Findings

1.      Isolated predominantly unconjugated hyperbilirubinemia

2.      Total serum bilirubin is usually mildly elevated and is typically below 5 mg/dL, although values fluctuate with precipitating factors.

3.      The conjugated bilirubin fraction is usually low, commonly less than about 20% of the total bilirubin.

4.      Normal:

o    AST

o    ALT

o    ALP

5.      Normal complete blood count

6.      No evidence of hemolysis, with expected findings including:

o    Normal reticulocyte count

o    Normal lactate dehydrogenase

o    Normal haptoglobin

o    Normal peripheral blood smear when obtained

In this patient, the calculated unconjugated bilirubin is 2.2 mg/dL, and the direct fraction is approximately 8% of the total bilirubin, which is highly compatible with Gilbert syndrome in the appropriate clinical setting.

5.2 Diagnostic Approach

The diagnosis is supported by:

1.      Persistent or intermittent isolated unconjugated hyperbilirubinemia

2.      Otherwise normal liver biochemical tests

3.      Absence of hemolysis

4.      Absence of clinical evidence for another hepatic or systemic disorder

5.      A typical history of bilirubin fluctuations associated with fasting, illness, dehydration, exertion, or stress

Provocative testing using prolonged fasting or medications is not recommended routinely.

If bilirubin elevation is atypical, progressive, predominantly conjugated, markedly elevated, or accompanied by abnormal liver enzymes or other clinical abnormalities, alternative diagnoses should be investigated.

5.3 Genetic Testing

Routine UGT1A1 genetic testing is not required when the clinical and laboratory pattern is typical.

Genetic testing may be considered when:

1.      The diagnosis remains uncertain

2.      The bilirubin level or clinical presentation is atypical

3.      Genetic counseling is required

4.      UGT1A1 genotyping is being considered for pharmacogenetic purposes before use of specific UGT1A1-dependent medications, according to drug-specific guidance

6. Differential Diagnosis

Important causes of unconjugated hyperbilirubinemia include:

6.1 Hemolysis

1.      Autoimmune hemolytic anemia

2.      G6PD deficiency

3.      Hereditary spherocytosis

4.      Other hereditary or acquired hemolytic disorders

Hemolysis is usually accompanied by one or more of the following:

·         Reticulocytosis

·         Elevated LDH

·         Reduced haptoglobin

·         Abnormal peripheral blood smear

6.2 Crigler-Najjar Syndrome

Crigler-Najjar syndrome results from a much more severe reduction or absence of UGT1A1 activity and generally produces substantially higher unconjugated bilirubin concentrations than Gilbert syndrome.

6.3 Other Causes

1.      Ineffective erythropoiesis

2.      Resorption of a large hematoma

3.      Drug-related impairment of hepatic bilirubin uptake

4.      Drug-related impairment of bilirubin conjugation

Other hepatobiliary disorders should be considered when liver enzymes, clinical findings, or the bilirubin pattern are not typical of Gilbert syndrome.

7. Management

7.1 General Management

1.      No specific treatment is required.

2.      Provide reassurance regarding the benign nature of the disorder.

3.      No special diet is required.

4.      Normal physical activity is appropriate.

5.      Avoid prolonged fasting and significant dehydration when practical.

6.      Routine liver imaging, liver biopsy, and repeated extensive investigations are unnecessary when the clinical and laboratory pattern is typical.

7.      Gilbert syndrome does not progress to cirrhosis or liver failure.

7.2 Medication Considerations

Reduced UGT1A1 activity can alter the handling of certain medications.

Irinotecan

UGT1A1 glucuronidates SN-38, the active metabolite of irinotecan.

Reduced-function UGT1A1 genotypes associated with Gilbert syndrome can increase susceptibility to irinotecan toxicity by increasing systemic exposure to SN-38.

Potential toxicities include:

1.      Severe neutropenia

2.      Diarrhea

The degree of risk depends on the specific UGT1A1 genotype, irinotecan exposure, and other clinical factors. The diagnosis of Gilbert syndrome alone does not determine irinotecan toxicity risk.

Atazanavir

Atazanavir inhibits UGT1A1 and may produce or accentuate unconjugated hyperbilirubinemia, particularly in individuals with reduced UGT1A1 activity.

This bilirubin elevation is generally related to impaired bilirubin conjugation and does not by itself indicate hepatocellular injury.

8. Key Clinical Insight

A young patient with mild isolated predominantly unconjugated hyperbilirubinemia, normal AST, ALT, and ALP, no evidence of hemolysis, and intermittent scleral icterus precipitated by fasting, illness, dehydration, exertion, or stress strongly suggests Gilbert syndrome.

In this patient, the predominantly unconjugated bilirubin elevation, normal liver enzymes, normal hemolysis markers, young age, and recent examination-related stress make Gilbert syndrome the most likely diagnosis.

References

1.      Bosma PJ, Chowdhury JR, Bakker C, Gantla S, de Boer A, Oostra BA, et al. The genetic basis of the reduced expression of bilirubin UDP-glucuronosyltransferase 1 in Gilbert's syndrome. New England Journal of Medicine. 1995;333(18):1171-1175. doi:10.1056/NEJM199511023331802.

2.      VanWagner LB, Green RM. Evaluating elevated bilirubin levels in asymptomatic adults. JAMA. 2015;313(5):516-517. doi:10.1001/jama.2014.12835.

3.      Memon N, Weinberger BI, Hegyi T, Aleksunes LM. Inherited disorders of bilirubin clearance. Pediatric Research. 2016;79(3):378-386. doi:10.1038/pr.2015.247.