Brainstem Anatomy Mnemonics

In 2005, Peter Gates published a superb paper titled:

‘The rule of 4 of the brainstem: a simplified method for understanding brainstem anatomy and brainstem vascular syndromes for the non-neurologist’.

Gates described a simplified method for answering the question ‘Where is the lesion?’ using only the parts of the brainstem that we actually examine during a clinical examination to understand brainstem vascular syndromes.
Firstly, a quick review of the blood supply of the brainstem. Simply put the blood supply comes from:

1. paramedian branches
2. long circumferential branches (SAP)

• superior cerebellar artery (SCA)
• anterior inferior cerebellar artery (AICA)
• posterior inferior cerebellar artery (PICA)

And occlusion of these two groups of vessels results in two distinct types of brainstem syndrome:

1. medial (or paramedian) brainstem syndromes
   ( due to para-median branch occlusion)
2. lateral brainstem syndromes
   ( due to occlusion of the circumferential branches, also occasionally seen in unilateral vertebral occlusion)

And now the rules. If you can remember these rules the  diagnosis of brainstem vascular syndromes becomes a pitifully simple exercise (?!) - here’s how it works:

In the rule of 4 there are 4 rules

1. There are 4 structures in the ‘midline‘ beginning with M
2. There are 4 structures to the ‘side‘ (lateral) beginning with S
3. There are 4 cranial nerves in the medulla, 4 in the pons and 4 above the pons (2 in the midbrain)
4. The 4 motor nuclei that are in the midline are those that divide equally into 12 except for 1 and 2, that is 3, 4, 6 and 12
   (5, 7, 9 and 11 are in the lateral brainstem)

The 4 medial structures and the associated deficits are:

1. Motor pathway (or corticospinal tract):
   contralateral weakness of the arm and leg
2. Medial Lemniscus:
   contralateral loss of vibration and proprioception in the arm and leg
3. Medial longitudinal fasciculus:
   ipsilateral inter-nuclear ophthalmoplegia
   (failure of adduction of the ipsilateral eye towards the nose and nystagmus in the opposite eye as it looks laterally)
4. Motor nucleus and nerve:
   ipsilateral loss of the cranial nerve that is affected (3, 4, 6 or 12)

The 4 ’side’ (lateral) structures and the associated deficits are:

1. Spinocerebellar pathway:
   ipsilateral ataxia of the arm and leg
2. Spinothalamic pathway:
   contralateral alteration of pain and temperature affecting the arm, leg and rarely the trunk
3. Sensory nucleus of the 5th cranial nerve:
   ipsilateral alteration of pain and temperature on the face in the distribution
   of the 5th cranial nerve
   (this nucleus is a long vertical structure that extends in the lateral aspect of the pons down into the medulla)
4. Sympathetic pathway:
   ipsilateral Homer’s syndrome, that is partial ptosis and a small pupil (miosis)

According to Gates:

These pathways pass through the entire length of the brainstem and can be likened to ‘meridians of longitude‘ whereas the various cranial nerves can be regarded as ‘parallels of latitude‘. If you establish where the meridians of longitude and parallels of latitude intersect then you have established the site of the lesion.

The 4 cranial nerves in the medulla are CN9-12:

1. Glossopharyngeal (CN9):
   ipsilateral loss of pharyngeal sensation
2. Vagus (CN10):
   ipsilateral palatal weakness
3. Spinal accessory (CN11):
   ipsilateral weakness of the trapezius and stemocleidomastoid muscles
4. Hypoglossal (CN12):
   ipsilateral weakness of the tongue The 12th cranial nerve is the motor nerve in the midline of the medulla. Although the 9th, 10th and 11th cranial nerves have motor components, they do not divide evenly into 12 (using our rule) and are thus not the medial motor nerves.

The 4 cranial nerves in the pons are CN5-8:

1. Trigeminal (CN5):
   ipsilateral alteration of pain, temperature and light touch on the face back as far as the anterior two-thirds of the scalp and sparing the angle of the jaw.
2. Abducent (CN6):
   ipsilateral weakness of abduction (lateral movement) of the eye (lateral rectus).
3. Facial (CN7):
   ipsilateral facial weakness.
4. Auditory (CN8):
   ipsilateral deafness. The 6th cranial nerve is the motor nerve in the medial pons.
   The 7th is a motor nerve but it also carries pathways of taste, and using the rule of 4 it does not divide equally in to 12 and thus it is not a motor nerve that is in the midline.
   The vestibular portion of the 8th nerve is not included in order to keep the concept simple and to avoid confusion. Nausea and vomiting and vertigo are often more common with involvement of the vestibular connections in the lateral medulla.

The 4 cranial nerves above the pons are CN1-4:

1. Olfactory (CN1):
   not in midbrain.
2. Optic (CN2):
   not in midbrain.
3. Oculomotor (CN3):
   impaired adduction, supradduction and infradduction of the ipsilateral eye with or without a dilated pupil.
   The eye is turned out and slightly down.
4. Trochlear (CN4):
   eye unable to look down when the eye is looking in towards the nose (superior oblique). The 3rd and 4th cranial nerves are the motor nerves in the midbrain.

Thus a medial brainstem syndrome will consist of the 4 M’s and the relevant motor cranial nerves, and a lateral brainstem syndrome will consist of the 4 S’s and either
the 9-11th cranial nerve if the lesion is in the medulla, or the 5th, 7th and 8th cranial nerve if the lesion is in the pons.

Handy tip:
If there are signs of both a lateral and a medial (paramedian) brainstem syndrome, then one needs to consider a basilar artery problem, possibly an occlusion.

I’ll let you mull over these rules until the next ‘brainstem’ post, where you’ll be able to test drive ‘Gates’ Brainstem Rules of 4′ on some clinical scenarios.
References
Gates, P. The rule of 4 of the brainstem: a simplified method for understanding brainstem anatomy and brainstem vascular syndromes for the non-neurologist. Internal Medicine Journal 2005; 35: 263-266 [pubmed]
Goldberg, S. Clinical Neuroanatomy Made Ridiculously Simple. MedMaster Series, 2000 Edition. [betterworldbooks]

Difference between acute pyelonephritis and Uncomplicated UTI are all except

Question 90

Difference between acute pyelonephritis and Uncomplicated UTI are all except

a.       Loss of Concentrating ability

b.      Presence of White blood casts

c.       Presence of Antibody against Tamm-Horsfall proteins of tubules

d.      Bacterial colony Count more than 10⁸

Answer

d. Bacterial colony Count more than 10⁸

Reference:

Harrison 16^th Edition Page 1717

Journal reference : 

a.       P. LARSSON, A. FASTH, U. JODAL, A. SOHL ÅKERLUND, C. SVANBORG EDÉN (1978) : URINARY TRACT INFECTIONS CAUSED BY PROTEUS MIRABILIS IN CHILDREN The Antibody Response to O and H Antigens and Tamm-Horsfall Protein and Bacterial Adherence to Uro-epithelium . Acta Paediatrica 67 (5), 591–596. doi:10.1111/j.1651-2227.1978.tb17807.x

b.      Kidney International (1976) 9, 23–29; doi:10.1038/ki.1976.3. Experimental pyelonephritis: The effect of chronic active pyelonephritis on renal function. Thomas E Miller1, David Layzell1 and Elaine Stewart1

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Normal urine is sterile.  UTI can therefore be diagnosed if a single viable gram negative bacterium inhabits the urinary tract (kidney, ureters, bladder).  In reality, the bacteria causing UTI multiply in log phase growth in normal urine, and most people with urinary tract infection have 10⁴-10⁶ bacteria/ml.  The acute number will depend on the urine flow rate, characteristics of the urine, the duration of infection, etc.  The problem in diagnosis is that of contamination arising from voided specimens passing through the non-sterile distal urethra.  For this reason, clinicians use the criteria of 10⁵ bacteria/ml of “clean catch” urine to diagnose UTI.  At this level, < 1% of the represent contaminants.  At counts of 1000-10,000/ml, there is a 50/50 chance the result represents contamination.  Such a count may represent true infection, but to be sure a second culture showing the same organism might be more convincing.  The second criteria for diagnosing UTI is the presence of pyuria (> 5 WBC/HPF) on the urinalysis.

Explanation

a.       A severe loss of urine concentrating capacity was demonstrable when the maximum urinary osmolality of a group of cases with pyelonephritis was compared with controls. Concentrating capacity decreased sharply over the first month but further loss over an eight-month period was minimal.

b.      Presence of White blood casts is Pathognomic for Pyelonephritis

c.       Presence of Antibody against Tamm-Horsfall proteins of tubules . "An increase in antibody levels against O antigen and Tamm-Horsfall protein was noted only in patients with acute pyelonephritis indicating that antibody determinations can be useful in differentiating between upper and lower urinary tract infection caused by Proteus in similarity to those caused by E. coli"

d.      Bacterial colony Count more than 10⁸

Comments : This is what the Journal Says : Sera from seven girls with acute symptomatic pyelonephritis and nine children with acute symptomatic cystitis caused by Proteus mirabilis were analysed for antibodies against the bacterial O and H1 antigens and the Tamm-Horsfall protein. An increase in antibody levels against O antigen and Tamm-Horsfall protein was noted only in patients with acute pyelonephritis indicating that antibody determinations can be useful in differentiating between upper and lower urinary tract infection caused by Proteus in similarity to those caused by E. coli. In contrast no difference in adhesive ability was noted comparing Proteus strains causing acute pyelonephritis or cystitis.

Remarks

If you have a better TEXTBOOK, reference, please send a mail to bruno@nellaimedicos.com

Thymoma commonly presents with Myasthenia Gravis

Question 89

Thymoma commonly presents with

a.       Myasthenia Gravis

b.      ??

c.       ??

d.       ??

Answer

a. Myasthenia Gravis

Reference

Harrison 16^th Edition Page

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Myasthenia gravis (MG) is an acquired autoimmune disorder characterized clinically by weakness of skeletal muscles and fatigability on exertion. Thomas Willis reported the first clinical description in 1672.

The antibodies in MG are directed toward the acetylcholine receptor (AChR) at the neuromuscular junction (NMJ) of skeletal muscles.

Explanation

The exact mechanism of loss of immunologic tolerance to AChR, a self antigen, is not understood. MG can be considered a B cell–mediated disease, as antibodies (a B cell product) against AChR are responsible for the disease. However, the importance of T cells in pathogenesis of MG is becoming increasingly apparent. The thymus is the central organ in T cell–mediated immunity, and thymic abnormalities such as thymic hyperplasia or thymoma are well recognized in myasthenic patients.

Comments

Since this question is often repeated, every one attempted it in a jiffy that they could not even recollect the other choices afterwards

Tips

Ä     MG is idiopathic in most patients.

Ä     Penicillamine is known to induce various autoimmune disorders, including MG.

Most common islet cell tumour in MEN 1 is Gastrinoma

Question 88

Most common islet cell tumour in MEN 1 is

a.       Gastrinoma

b.      Insulinoma

c.       Glucagonoma

d.      Somatostatinoma

Answer

a. Gastrinoma

Reference

Schwartz 7^th Edition Page 1686

Sabiston 15^th Edition Page 685

Harrison 16^th Edition Page 2231

Robbins 5^th Edition Page 1170

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Neoplasia of the pancreatic islets is the second most common manifestation of MEN 1 and tends to occur in parallel with hyperparathyroidism. Increased pancreatic islet cell hormones include pancreatic polypeptide (75 to 85%), gastrin [60%; Zollinger-Ellison syndrome (ZES)], insulin (25 to 35%), vasoactive intestinal peptide (VIP) (3 to 5%; Verner-Morrison or watery diarrhea syndrome), glucagon (5 to 10%), and somatostatin (1 to 5%). The tumors rarely produce adrenocorticotropin (ACTH), corticotropin-releasing hormone (CRH), growth hormone-releasing hormone (GHRH), calcitonin gene products, neurotensin, gastric inhibitory peptide, and others. Many of the tumors produce more than one peptide. The pancreatic neoplasms differ from the other components of MEN 1 in that approximately one-third of the tumors display malignant features, including hepatic metastases (Chap. 93).

Explanation

Of the choices given, the most Common Pancreatic Tumour in MEN I is Gastrinoma.

Comments

Multiple Endocrine Neoplasia (MEN) Syndromes
Type	MEN 1	MEN 2		Mixed Syndromes
		MEN 2A	MEN 2B
Name	Wermer’s Syndrome	Sipple’s Syndrome
Gene	11q 11-13	RET
Parathyroid	Parathyroid hyperplasia or adenoma	Parathyroid hyperplasia or adenoma		Familial pheochromocytoma and islet cell tumor von Hippel-Lindau syndrome, pheochromocytoma, and islet cell tumor Neurofibromatosis with features of MEN 1 or 2 Myxomas, spotty pigmentation, and generalized endocrine overactivity in a single family
Pancreas	Islet cell hyperplasia, adenoma, or carcinoma
Pituitary	Pituitary hyperplasia or adenoma
Thyroid	C Cell Hyperplasia	Medullary Thyroid Carcinoma	MTC
Adrenal	Rarely Cortical Involvement	Pheochromocytoma	Pheochromocytoma
Others	Other less common manifestations: foregut carcinoid, , subcutaneous or visceral lipomas, dermal angiofibromas or collagenomas	Cutaneous lichen amyloidosis Hirschsprung disease Familial Medullary Thyroid Carcinoma	Mucosal and gastrointestinal neuromas Marfanoid features

Tips

This is one of the most repeated topics for AIPG. There will be 2 to 3 questions every year

MEN

Ä     Pancreatic islet cell tumors are diagnosed by identification of a characteristic clinical syndrome, hormonal assays with or without provocative stimuli, or radiographic techniques. One approach involves annual screening of people at risk with measurement of basal and meal-stimulated levels of pancreatic polypeptide to identify the tumors as early as possible; the rationale of this screening strategy is the concept that surgical removal of islet cell tumors at an early stage will be curative. Other approaches to screening include measurement of serum gastrin and pancreatic polypeptide levels every 2 to 3 years, with the rationale that pancreatic neoplasms will be detected at a later stage but can be managed medically, if possible, or by surgery. High-resolution, early-phase computed tomography (CT) scanning provides the best noninvasive technique for identification of these tumors, but intraoperative ultrasonography is the most sensitive method for detection of small tumors.

Ä     ZES is caused by excessive gastrin production and occurs in more than half of MEN 1 patients with pancreatic islet cell tumors. Clinical features include increased gastric acid production, recurrent peptic ulcers, diarrhea, and esophagitis. The ulcer diathesis is refractory to conservative therapy such as antacids. The diagnosis is made by finding increased gastric acid secretion, elevated basal gastrin levels in serum [generally >115 pmol/L (200 pg/mL)], and an exaggerated response of serum gastrin to either secretin or calcium. Other causes of elevated serum gastrin levels, such as achlorhydria, treatment with H2 receptor antagonists or omeprazole, retained gastric antrum, small-bowel resection, gastric outlet obstruction, and hypercalcemia, should be excluded. Gastrin-producing carcinoid-like tumors are frequently present in the duodenal wall.

Ä     Insulinoma causes hypoglycemia in about one-third of MEN 1 patients with pancreatic islet cell tumors. The tumors may be benign or malignant (25%). The diagnosis can be established by documenting hypoglycemia during a short fast with simultaneous inappropriate elevation of serum insulin and C-peptide levels. More commonly, it is necessary to subject the patient to a supervised 72-h fast to provoke hypoglycemia. Large insulinomas may be identified by CT scanning; small tumors not detected by radiographic techniques may be localized by selective arteriographic injection of calcium into each of the arteries that supply the pancreas and sampling the hepatic vein for insulin to determine the anatomic region containing the tumor. Intraoperative ultrasonography can also be used to localize these tumors, but preoperative calcium injection data are helpful in guiding the subtotal pancreatectomy if multiple or no abnormalities are detected by intraoperative ultrasonography.

Ä     Glucagonoma in occasional MEN 1 patients causes a syndrome of hyperglycemia, skin rash (necrolytic migratory erythema), anorexia, glossitis, anemia, depression, diarrhea, and venous thrombosis. In about half of these patients the plasma glucagon level is high, leading to its designation as the glucagonoma syndrome, although elevation of plasma glucagon level in MEN 1 patients is not necessarily associated with these symptoms. The glucagonoma syndrome may represent a complex interaction between glucagon overproduction and the nutritional status of the patient.

Ä     The Verner-Morrison or watery diarrhea syndrome consists of watery diarrhea, hypokalemia, hypochlorhydria, and metabolic acidosis. The diarrhea can be voluminous and is almost always found in association with an islet cell tumor, prompting use of the term pancreatic cholera. However, the syndrome is not restricted to pancreatic islet tumors and has been observed with carcinoids or other tumors. This syndrome is believed to be due to overproduction of VIP, although plasma VIP levels may not be elevated. Hypercalcemia may be induced by the effects of VIP on bone as well as by hyperparathyroidism.

Conn’s Syndrome is Adrenal Adenoma

Question 87

Conn’s Syndrome is 

a.       Adrenal hyperplasia

b.      Adrenal carcinoma

c.       Adrenal adenoma

d.      None of the above

Answer

c. Adrenal Adenoma.

Reference:

Harrison 16^th Edition Page 2138

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In the original case of excessive and inappropriate aldosterone production, the disease was the result of an aldosterone-producing adrenal adenoma (Conn's syndrome). Most cases involve a unilateral adenoma, which is usually small and may occur on either side.

Explanation

Self Explanatory. Though Hyperaldosteronism can be due to many causes, an aldosterone producing adrenal adenoma is called as Conn’s Disease

Comments

Rarely, primary aldosteronism is due to an adrenal carcinoma. Aldosteronism is twice as common in women as in men, usually occurs between the ages of 30 and 50, and is present in approximately 1% of unselected hypertensive patients. However, the prevalence may be as high as 10%, depending on the criteria and study population. Most of this difference is not secondary to the prevalence of patients with an aldosteronoma but rather because of the inclusion of those with bilateral hyperplasia.

In many patients with clinical and biochemical features of primary aldosteronism, a solitary adenoma is not found at surgery. Instead, these patients have bilateral cortical nodular hyperplasia. In the literature, this disease is also termed idiopathic hyperaldosteronism, and/or nodular hyperplasia. The cause is unknown

Tips

High blood pressure (hypertension) is the main, and often the only, symptom.

Other symptoms may occur because high aldosterone levels in the blood act on the kidney to increase the loss of the mineral potassium in the urine. This in turn may lead to a fall in blood potassium, resulting in tiredness, muscle weakness and passing of large volumes of urine (polyuria), especially at night (nocturia). However, these symptoms are also found in many other conditions (for example, diabetes mellitus or hypercalcaemia) and do not, by themselves, establish a diagnosis of Conn's syndrome. Also, many patients with proven Conn's syndrome do not have a low blood potassium level.