Hospital Medicine

Benign paroxysmal positional vertigo (benign paroxysmal nystagmus)

Jump to Section

Benign paroxysmal positional vertigo (benign paroxysmal nystagmus)

I. What every physician needs to know.

Dizziness as a primary complaint accounts for 3-4% of all emergency room (ER) visits, amounting to over 150,000 ER visits annually in the United States. Close to 20% of dizzy patients are admitted to the hospital and over a third are diagnosed with peripheral vestibular disorders. In fact, vestibular disease tops the list of final diagnoses found in ER patients presenting with dizziness. Fortunately, 90% of dizzy patients have an attributable diagnosis and 75% of the time the etiology can be revealed by history and physical examination alone.

Classically, physicians were taught that the patient’s description of dizziness, vertigo (sense of spinning or motion), pre-syncope, lightheadedness, unsteadiness, is diagnostically useful information (i.e., the differential diagnoses list differs for a complaint of vertigo versus lightheadedness). However, a study of more than 300 consecutive patients presenting to the ED with acute dizziness found that more than half were unable to reliably report which type of dizziness best describes their symptom and the type of dizziness was not a reliable predictor of the underlying cause. The current paradigm groups the causes of acute dizziness into three vestibular syndromes based on the timing and triggers of the symptom. The use of the term vestibular refers to the symptom of dizziness and does not imply underlying cause.

  1. Triggered, episodic vestibular syndrome (t-EVS) is characterized by repetitive episodes of dizziness triggered by an event. Patients are asymptomatic at rest. Benign paroxysmal positional vertigo (BPPV) is the most common condition that causes t-EVS.

  2. Spontaneous episodic vestibular syndrome (s-EVS) presents as recurrent episodes of dizziness lasting minutes to hours. Although there appear to be predisposing factors (e.g.: environmental or lifestyle factors in vestibular migraine), there is no clear trigger.

  3. Acute Vestibular Syndrome (AVS) is a monophasic, abrupt-onset dizziness that persists for days. It is distinguished from t-EVS in that the dizziness is continuous at rest and is exacerbated, but not triggered by movement.

Defining the type of vestibular syndrome is key to the choice and interpretation of physical examination.

BPPV, also known as benign positional vertigo and benign paroxysmal nystagmus, is the most common of the peripheral vestibulopathies and has a lifetime prevalence of 2.4%. BPPV is characterized by brief episodes of intense vertigo that is triggered by changing head position.

The pathophysiology of BPPV is well documented from intraoperative observations of free-floating debris in the posterior semicircular canal of the inner ear vestibular system.

This forms the basis for treatment with canalith repositioning maneuvers (CRM) described below.

The vestibular apparatus consists of the utricle, the saccule and three endolymph-containing semicircular canals that arise from their individual ampullae. The ampulla contain a gelatinous mass called the cupula which is attached to polarized hair cells (Figure 1). The utricle and saccule contain otoliths that are situated atop hair cells embedded in a gelatinous material. Linear and vertical accelerations of the head move the otoliths, which tilt the hair cells informing the brain of motion (Figure 2).

Figure 1.

The vestibular system.

Figure 2.


Figure 3.

Head impulse test

Figure 4.

Test of skew.

Rotational movements are transmitted by endolymph circulation within three semicircular canals: anterior (superior), lateral (horizontal) and posterior. The direction and force of the endolymph circulation is transmitted to a membrane of hair cells located in the base of each canal, the ampullae.

BPPV occurs when the otoliths fall from the utricle into any one of the semicircular canals inducing symptoms of exaggerated motion. Because the posterior semicircular canal is in the most dependent position, most (60-90%) of BPPV cases involve the posterior canal (PC). The incidence of horizontal canal (HC) BPPV (5-30%) is probably underestimated because it is more likely than PC BPPV to remit spontaneously. Anterior canal involvement is thought to be rare. Provocative physical examination maneuvers (e.g., the Dix-Hallpike), and canalith repositioning maneuvers (e.g., the Epley), are aimed at moving the otoliths from the semicircular canal. Over 90% of cases is successfully treated with CRMs.

II. Diagnostic Confirmation: Are you sure your patient has benign paroxysmal positional vertigo?

A. History Part I: Pattern Recognition:

A case of BPPV was first described by Barany in 1921:

“The attacks only appeared when she lay on her right side. When she did this, there appeared a strong rotatory nystagmus to the right. The attack lasted about thirty seconds and was accompanied by violent vertigo and nausea. If, immediately after the cessation of these symptoms, the head was again turned to the right, no attack occurred, and in order to evoke a new attack in this way, the patient had to lie for some time on her back or on her left side.”

The diagnosis of BPPV is made clinically through careful interviewing and physical examination. Patients describe an illusory sensation of motion, either of themselves or of their surroundings. The sensation is often characterized as spinning, tilting or being pulled backwards. Patients may localize the affected ear by identifying the direction of movement that precipitates the attack (i.e., when turning to the right precipitates vertigo, the right ear is affected). Symptom quality proves less precise than the symptom timing and associated triggers.

The timing of BPPV is abrupt in onset, lasts briefly (a few seconds to a minute) and is episodic, although patients may overestimate the duration because of the subsequent nausea and disequilibrium that may follow. Patients often report that small amounts of actual motion are perceived as large movements, for example, a 20-degree turn of the head will feel like a 180 degree spin. Attacks tend to occur in clusters.

Attacks of PC BPPV are typically experienced as episodic vertigo with rapid positional changes of the head, particularly with neck extension (reaching for objects on shelves) and movements relative to gravity (lying down, sitting up from supine, bending over). Turning in bed from side to side provokes vertigo in patients with horizontal (HC) BPPV.

B. History Part 2: Prevalence:

BPPV occurs more commonly in women with a female to male ratio of 2:1 to 3: 1, and affects patients usually between their 5th and 7th decade. Older adults are at increased risk and in this population. BPPV may not be “benign” given its association with reduced ADL function, falls and depression. Furthermore, BPPV in older adults may coexist with other causes of dizziness.

50-70% of BPPV cases is idiopathic; idiopathic cases appear to be twice as common in women. The most common cause of secondary BPPV is head trauma, accounting for 7-17% of cases while vestibular neuritis has been implicated in 15% of cases. The right ear is more commonly affected likely due to the frequent habit of sleeping on the right side.

C. History Part 3: Competing diagnoses that can mimic benign paroxysmal positional vertigo.

The differential diagnoses for t-EVS vestibular syndrome include BPPV, orthostatic hypotension and posterior fossa mass lesions. A posterior circulation stroke can mimic BPPV, but more typically presents as AVS syndrome with persistent (rather than triggered and episodic) dizziness, severe imbalance; other neurologic and oculomotor signs and symptoms are typically present.

Anterior canal (AC) is rarely affected by BPPV. The Dix-Hallpike induces a downbeat and torsional nystagmus (upper poles of the eyes beating toward the involved ear). Given the rarity of AC BBPV and because positional downbeat nystagmus may be due to central lesions, these patients should be evaluated for a central process. Generally, central causes of positional vertigo should be considered when the pattern of nystagmus is persistently down beating, pure torsional, or when repeated canalith repositioning maneuvers fail to resolve symptoms and nystagmus.

Patients with BPPV may not describe vertigo, but endorse postural lightheadedness which may be misdiagnosed as orthostatic hypotension. Patients complaining of postural lightheadedness should be asked if lying supine or turning in bed induces symptoms (inconsistent with orthostasis) and orthostatic vital signs measured.

By defining the vestibular syndrome that best fits the patient’s clinical presentation, t-EVS or AVS, the clinician can appropriately target and interpret tests. In contrast to t-EVS characterized by episodic, dizziness triggered by head movement, patients with Acute Vestibular Syndrome present with rapid onset dizziness lasting days to weeks, gait unsteadiness, nausea, vomiting, and nystagmus. Vestibular neuritis or labyrinthitis is the most common cause of AVS, but posterior circulation stroke can be a serious mimic. In a cohort of patients with AVS who had at least one stroke risk factor, testing of eye movements for the Vesibulo-ocular reflex (VOR), skew deviation, and for nystagmus in different gaze positions have been reported to be more accurate for the diagnosis of stroke than early CT or MRI-DWI. The reader is referred to Vestibular Neuritis section.

Meniere’s disease is a syndrome characterized by recurrent spontaneous episodes of vertigo, sensorineural hearing loss in the affected ear, and fluctuating tinnitus and aural fullness. The vertigo is classically of longer duration than BPPV, often lasting 20 minutes to several hours, and is not provoked by position change. The tinnitus is classically low frequency, a roaring sound.

Other diagnostic possibilities to consider include medication toxicity, e.g., gentamicin, alcohol intoxication, vestibular migraine, carbon monoxide poisoning, central nervous system (CNS) tumors (acoustic neuroma), demyelinating diseases, and psychiatric illnesses.

D. Physical Examination Findings.

BPPV is diagnosed through careful history taking and positioning maneuvers that move the affected canal in the direction of maximum gravity, provoking transient vertigo and typical pattern of nystagmus. The Dix-Hallpike test is considered the gold standard for the diagnosis of PC-BPPV. The head movements that comprise the maneuver stimulate endolymph circulation in the posterior canal.

The patient should be asymptomatic prior to initiating the test. The patient should be informed of the upcoming movements and warned that they may experience a sudden onset of intense vertigo and/or nausea that should abate within 2 minutes. The table should be adjusted to allow for extension of the neck below the edge of the table. If this is not possible, a rolled towel under the patient's shoulder blade can ensure neck hyperextension.

To perform this maneuver, start with the suspected affected side. With the patient seated upright, turn the patient's head 45 degrees to the affected side. Maintain hands on the patient's head during the maneuver to support and maintain the 45-degree angle. Move the patient supine with the neck hyperextended, hanging off the edge of the bed approximately 20 degrees, affected ear down.

The patient should be asked if this reproduces their symptoms and the eyes should be observed for the onset of nystagmus. Typically there is a brief latency of nystagmus onset (usually 2-5 seconds). The nystagmus is rotatory with the fast phase beating towards the lower ear, resolves after 30 seconds to one minute, and fatigues with repeated testing. The patient should be returned to the upright position and the reversal of nystagmus direction may be observed. The other side should then be repeated (Figure 5). In BPPV patients who do not demonstrate nystagmus, but experience vertigo during the Dix-Hallpike test (an estimated one-fourth of BPPV cases), studies have shown CRMs to be highly effective.

Figure 5.

Dix-Hallpike test.

Caution should be taken if there is concern for vascular dissection and with patients that have a limited cervical range of motion, e.g., cervical stenosis, rheumatoid arthritis, ankylosing spondylitis.

If one suspects lateral/horizontal BPPV, the supine head roll or Pagnini-McClure test is performed. The patient lies supine with the head up facing in a central position. Quickly rotate the patient's head and body 90 degrees to one side so that the ear faces downward towards the bed. Observe the patient's eyes for nystagmus. When the nystagmus resolves or if there are no symptoms, return the head to the face up position. Turn 90 degrees to the other side and observe again for the presence of nystagmus. Lateral nystagmus that beats towards the ground (geotropic) or the ceiling (apogeotropic) is considered a positive test (Figure 6). The direction of roll that causes the more intense nystagmus often identifies the affected side.

Figure 6.

Supine head roll.

E. What diagnostic tests should be performed?

1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Laboratory tests have little role in the evaluation of BPPV. A systematic review of the diagnostic evaluation of dizziness which included 12 studies and over 4,500 patients found that laboratory abnormalities explained the etiology of dizziness in only 26 patients (3 electrolytes disturbances, 11 glucose, 11 anemia, 1 hypothyroid).

Electronystagmography (ENG) adds little to the diagnosis because it does not record torsional eye movements.

2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Imaging tests have little role in the evaluation of BPPV and is reserved when there are atypical or unusual features.

F. Over-utilized or "wasted" diagnostic tests associated with this diagnosis.


III. Default Management.

BPPV typically resolves spontaneously; a prospective longitudinal study reported a median time to resolution in untreated patients of 7 days in HC BPPV and 17 days in PC BPPV.

In 2008 an expert panel representing physicians from multiple disciplines including internal medicine, emergency medicine, geriatrics, otolaryngology, neurology, physical medicine, and rehabilitation published evidence based guidelines on the management of BPPV. They advised canalith repositioning maneuvers for the treatment of BPPV and recommended against medications for symptoms. Medications are used primarily for relief of severe nausea and vomiting.

The Academy of Neurology in the same year issued similar recommendations. Both cited that medications were no better than placebo and listed potential risks including sedation, falls and delayed symptom improvement. The Epley maneuver is the best-evidenced canalith repositioning technique to treat PC BPPV. Through a series of guided or self-directed movements, the dislodged canaliths move from the posterior semicircular canal back into the utricle. The success rate is approximately 80% after one treatment and increases to 92% after repeating up to four times.

To perform the Epley, start with the Dix-Hallpike on the side of the affected ear. Watch for the onset of nystagmus while the head is hyperextended. Once the nystagmus ceases or vertigo dissipates (at, least 30 seconds for each position), rotate the patient's head 90 degrees so they face the other side; the neck is still extended and the affected ear is now up. Continue in the direction of the unaffected side, turning the entire body including the shoulders, keeping the face down. Finally sit the patient up, holding the neck subtly flexed and chin pointed slightly downward. (Figure 7).

Figure 7.

Epley maneuver.

Caution should be taken when there is concern for vascular dissection and in patients that have a limited cervical range of motion, e.g., cervical stenosis, rheumatoid arthritis, ankylosing spondylitis.

The Semont maneuver may be used in lieu of the Epley maneuver in PC BPPV patients with limited neck extension. The patient is rapidly swung 180 degrees from lying on the affected side to lying on the unaffected side within 1.3 seconds.

In a review of 11 randomized trials of CRMs, Epley treated groups reported significantly higher rates of complete symptom resolution (OR of 4.42) compared with untreated patients. Furthermore, there was significant difference in the rate of conversion from a positive to a negative Dix Hallpike test favoring the treatment groups. There were no serious adverse effects from treatment and the only reported problem was the inability to tolerate the maneuvers due to vomiting or cervical spine problems. Two trials comparing two maneuvers, the Epley with the Semont maneuvers, found no difference in resolution of nystagmus. Brandt-Daroff maneuver, designed for symptom habituation is found to be less effective. One trial comparing the Epley maneuver to Brandt Daroff found 80% versus 25% resolution rates, respectively.

Post treatment head restriction appears not to offer significant additional benefit, although it may be prudent for patients to sit still in an upright position for 15 minutes after treatment. Patients can also perform the Epley at home, although clinician guidance has a higher success rate.

Treatments for HC BPPV do not boast the same success rates as for posterior canal repositioning. Fortunately HC disease resolves more quickly and spontaneously than posterior canal disease. Depending on the direction of nystagmus elicited by the head-roll test (geotropic versus apogeotropic), specific CRMs are used. The Lempert or barbeque roll (roll the patient 360 degrees while supine) is used to treat HC BPPV with geotropic nystagmus. An alternative treatment for HC BPPV is the forced prolonged position wherein the patient is instructed to lie with the unaffected ear down for several hours. Gufoni’s maneuver and head-shaking are other CRMs for treatment of HC BPPV. The Gufoni’s maneuver consists of first laying the patient down on the unaffected ear (maintaining this position for 1-2 minutes until the nystagmus subsides), quickly rotating the head 45 degrees toward the floor (maintaining this position for 2 minutes), then returning to an upright position. Head-shaking consists of turning the head from side to side at two cycles per second for 15 seconds. Refer to Table I.

Table I.

Summary of likelihood ratio for individual and combined tests.
Physical exam finding Likelihood ratio when exam is abnormal (likelihood of stroke is increased by this factor) Likelihood ratio when exam is normal (likelihood of stroke is decreased by this factor)
HINTS battery 17 0.01
Head impulse test 12 0.07
Direction changing nystagmus 3.3 0.80
Test of skew 8.5 0.78
Truncal ataxia 18 0.66

When pharmacotherapy is necessary to treat symptoms, vestibular suppressants and antiemetics are frequently administered. The major classes of vestibular suppressing medications are antihistamines, benzodiazepines, and anticholinergics. The vestibular suppressants with anticholinergic and antihistamine properties also have antiemetic activity. These drugs do not eliminate the vertigo, but reduce the severity of symptoms in the acute phase, when a patient may have severe nausea and vomiting. IV agents are usually preferable to oral agents. Antivertigo medications, if necessary in cases of severe nausea and vomiting, should be administered only during the first few days as they are sedating and may delay central compensation of the vestibular deficit.

Few studies have compared the efficacy of one agent over another. A double blind study which randomized 74 adult patients presenting with peripheral vertigo to dimenhydrinate 50 mg IV or Lorazepam 2 mg IV reported greater reduction in vertigo with dimenhydrinate. The ability to walk was judged to be better at one and two hours after treatment with dimenhydrinate. Patients treated with Lorazepam experienced more drowsiness.

Meclizine is the most frequently prescribed of the antihistamines in the United States and as a first generation histamine H1 blocker, it crosses the blood-brain barrier to disrupt the signal from the vestibular nucleus to the emetic center in the medulla. Meclizine is better studied for the treatment of Meniere's disease and two systematic reviews conducted on its efficacy concluded differently. One concluded a benefit over placebo, the other concluded the sum total of the trials were of insufficient quality to judge. There are no randomized controlled trials examining meclizine for the treatment of BPPV.

A. Immediate management.

Canalith repositioning maneuver specific to the semicircular canal affected is the treatment of choice for immediate management.

B. Physical Examination Tips to Guide Management.


C. Laboratory Tests to Monitor Response to and Adjustments in Management.


D. Long-term management.

Because BPPV is episodic and can recur at a rate of up to 15% per year, chronic management strategies are often needed. Vestibular therapy is a form of rehabilitation designed to promote habituation, adaptation and compensation for chronic symptoms. Programs include canalith repositioning, adaptation exercises for gaze stabilization and postural control exercises for fall prevention. Based on a Cochrane review, CRMs have more supportive evidence compared with vestibular rehabilitation exercises for short term treatment, but the combination of the two types of treatment is effective for long-term recovery from BPPV symptoms.

E. Common Pitfalls and Side-Effects of Management.


IV. Management with Co-Morbidities.

Particular care should be paid to older adult patients with BPPV because co-morbid conditions, such as visual impairment, proprioceptive deficits and polypharmacy contribute to a greater functional impact of both BPPV and sedating pharmacotherapy. Elderly patients who suffer from BPPV have a greater incidence of falls. Therefore, any treatment strategy should include a fall risk and gait safety assessment and avoidance of medications that exacerbate the risk.

A. Renal Insufficiency.

No change in standard management.

B. Liver insufficiency.

No change in standard management.

C. Systolic and Diastolic Heart Failure.

No change in standard management.

D. Coronary Artery Disease or Peripheral Vascular Disease.

No change in standard management.

E. Diabetes or other Endocrine issues.

No change in standard management.

F. Malignancy.

No change in standard management.

G. Immunosuppression (HIV, chronic steroids, etc.).

No change in standard management.

H. Primary Lung Disease (COPD, Asthma, ILD).

No change in standard management.

I. Gastrointestinal or Nutrition Issues.

No change in standard management.

J. Hematologic or Coagulation Issues.

No change in standard management.

K. Dementia or Psychiatric Illness/Treatment.

Avoid the use of sedating and anticholinergic medications as this could exacerbate psychiatric symptoms and/or increase the risk of falls.

V. Transitions of Care.

A. Sign-out Considerations While Hospitalized.


B. Anticipated Length of Stay.


C. When is the Patient Ready for Discharge?


D. Arranging for Clinic Follow-up.


1. When should clinic follow up be arranged and with whom?


2. What tests should be conducted prior to discharge to enable best clinic first visit?


3. What tests should be ordered as an outpatient prior to, or on the day of, the clinic visit?


E. Placement considerations.


F. Prognosis and Patient Counseling.


VI. Patient Safety and Quality Measures.

For older patients, patients with neuromuscular and joint disorders, patients with osteoporosis at risk for fragility fracture, it is recommended that an assessment for gait and fall risk is performed prior to discharge. The use of benzodiazepines may worsen falls risk and should be avoided.

A. Core Indicator Standards and Documentation.


B. Appropriate Prophylaxis and Other Measures to Prevent Readmission.


VII. What's the evidence?

Newman-Toker, D, Hsieh, Y, Camargo, C. "Spectrum of Dizziness Visits to US Emergency Departments: Cross Sectional Analysis from a Nationally Representative Sample". Mayo Clinic Proceedings. vol. 83. July 2008. pp. 765-775.

Hoffman, R, Einstadter, D, Kroenke, K. "Evaluating Dizziness". American Journal of Medicine. vol. 107. Nov 1999. pp. 468-478.

Newman-Toker, D., Cannon, L., Stofferahn, M. "Imprecision in Patients Reports of Dizziness Symptom Quality: A Cross-sectional study conducted in an Acute Care Setting". Mayo Clinic Proceedings. vol. 82. Nov 2007. pp. 1329-1340.

Kattah, J, Talkad, A, Wang, D, Hsieh, Y, Newman-Toker, D. "HINTS to Diagnose Stroke in the Acute Vestibular Syndrome". Stroke. vol. 40. 2009. pp. 3504-3510.

Bhattacharyya. "Clinical Practice Guideline: Benign Paroxysmal Positional Vertigo". Otolaryngology -Head and Neck Surgery. vol. 139. 2008. pp. 81.

Fife. "Practice Parameter: Therapies for benign paroxysmal positional vertigo (an evidence based review)". Neurology. vol. 70. May 2008. pp. 2067-2074.

Gordan, C, Gadoth, G. "Repeated vs single physical maneuver in benign paroxysmal positional vertigo". Acta Neurologica Scandinvica. March 2004. pp. 166-169.

Hillier, S, McDonnell, M. "Vestibular rehabilitation for unilateral peripheral vestibular dysfunction". Cochrane Database of Systematic Reviews. 2011.

Marchetti, G, Whitney, S. "Older adults and balance dysfunction". Neurologic Clin. vol. 23. 2005. pp. 785-805.

Radtke, A, Von Brevern, M, Tiel-Wilk, K. "Self Treatment of Benign Paroxysmal Positional Vertigo". Neurology. vol. 63. 2004. pp. 15-152.

Furman, J, Cass, S. "Benign Paroxysmal Positional Vertigo". New England Journal of Medicine. vol. 341. Nov 1999. pp. 1590-1596.

Li, J, Epley, J. "The 360 Degree maneuver for Treatment of Benign Positional Vertigo". Otology and Neurology. vol. 27. 2006. pp. 71-77.

McGee, S. "Working Up the Dizzy Patient. Oral presentation at National ACP". Internal Medicine. April 2011.

Edlow, J., Newman-Toker, D.. "Using the Physical Examination to Diagnose Patients with Acute Dizziness and Vertigo". Journal of Emergency Medicine. vol. 50. 2016. pp. 617-628.

(Presents a paradigm for evaluating acute dizziness that categorizes the vestibular syndromes based on timing and trigger of the symptoms and specifies the choice of bedside examination based on the clinical syndrome.)

Kerber, KA.. "Vertigo and Dizziness in the Emergency Department". Emerg Med Clin North Am. vol. 27. 2009. pp. 39.

(Describes features of and pitfalls in management of vestibular neuritis, BPPV, and Meniere’s disease, each representing a common cause of 3 categories of vestibular syndromes.)

McDonnell. "Vestibular Rehabilitation for unilateral peripheral vestibular dysfunction". Cochrane Database of Systematic Reviews. 2015.

(Systematically reviews randomized trials assessing the effectiveness of vestibular rehabilitation for symptomatic unilateral peripheral vestibular dysfunction in community dwelling adults.)

Kim, Ji-Soo, Zee, David. "Benign Paroxysmal Positional Vertigo". N Engl J Med. vol. 370. 2014. pp. 1138-47.

(Provides a clinical review of the diagnosis and treatment of PC and HC BPPV.)

Hilton. Cochrane Database of Systematic Reviews.

(Systematically reviews the effectiveness of the Epley maneuver for the treatment of PC BPPV when compared to placebo and other canalith repositioning maneuvers.)

Related Resources

You must be a registered member of Cancer Therapy Advisor to post a comment.

Regimen and Drug Listings


Bone Cancer Regimens Drugs
Brain Cancer Regimens Drugs
Breast Cancer Regimens Drugs
Endocrine Cancer Regimens Drugs
Gastrointestinal Cancer Regimens Drugs
Gynecologic Cancer Regimens Drugs
Head and Neck Cancer Regimens Drugs
Hematologic Cancer Regimens Drugs
Lung Cancer Regimens Drugs
Other Cancers Regimens
Prostate Cancer Regimens Drugs
Rare Cancers Regimens
Renal Cell Carcinoma Regimens Drugs
Skin Cancer Regimens Drugs
Urologic Cancers Regimens Drugs

Sign Up for Free e-newsletters